Dome

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For other uses, see Dome (disambiguation).
"Domal" redirects here. For "domal consonants", see Retroflex consonant.
Dome of St. Peter's Basilica in Rome crowned by a cupola. Designed primarily by Michelangelo, the dome was not completed until 1590
Fiberglass dome cottage in Davis, California. This dome was built in 1972 and is part of the Baggin's End student housing cooperative.

A dome is an element of architecture that resembles the hollow upper half of a sphere. Dome structures made of various materials have a long architectural lineage extending into prehistory.

Corbel domes and true domes have been found in the ancient Middle East in modest buildings and tombs. The construction of the first technically advanced true domes began in the Roman Architectural Revolution,[1] when they were frequently used by the Romans to shape large interior spaces of temples and public buildings, such as the Pantheon. This tradition continued unabated after the adoption of Christianity in the Byzantine (East Roman) religious and secular architecture, culminating in the revolutionary pendentive dome of the 6th-century church Hagia Sophia. Squinches, the technique of making a transition from a square shaped room to a circular dome, was most likely invented by the ancient Persians. The Sassanid Empire initiated the construction of the first large-scale domes in Persia, with such royal buildings as the Palace of Ardashir, Sarvestan and Ghal'eh Dokhtar. With the Muslim conquest of Greek-Roman Syria, the Byzantine architectural style became a major influence on Muslim societies. Indeed the use of domes as a feature of Islamic architecture has gotten its roots from Roman Greater-Syria (see Dome of the Rock).

An original tradition of using multiple domes was developed in the church architecture in Russia, which had adopted Orthodox Christianity from Byzantium. Russian domes are often gilded or brightly painted, and typically have a carcass and an outer shell made of wood or metal. The onion dome became another distinctive feature in the Russian architecture, often in combination with the tented roof.

Domes in Western Europe became popular again during the Renaissance period, reaching a zenith in popularity during the early 18th century Baroque period. Reminiscent of the Roman senate, during the 19th century they became a feature of grand civic architecture. As a domestic feature the dome is less common, tending only to be a feature of the grandest houses and palaces during the Baroque period.

Construction of domes in the Muslim world reached its peak during the 16th – 18th centuries, when the Ottoman, Safavid and Mughal Empires, ruling an area of the World compromising North Africa, the Middle East and South- and Central Asia, applied lofty domes to their religious buildings to create a sense of heavenly transcendence. The Sultan Ahmed Mosque, the Shah Mosque and the Badshahi Mosque are primary examples of this style of architecture.

Many domes, particularly those from the Renaissance and Baroque periods of architecture, are crowned by a lantern or cupola, a Medieval innovation which not only serves to admit light and vent air, but gives an extra dimension to the decorated interior of the dome.

Etymology[edit]

The English word "dome" ultimately derives from the Greek and Latin domus, which was used up through the Renaissance to label a revered house, such as a Domus Dei, or "House of God", regardless of the shape of its roof. This is reflected in the uses of the Italian word duomo, the German/Icelandic/Danish word dom ("cathedral"), and the English word dome as late as 1656, when it meant a "Town-House, Guild-Hall, State-House, and Meeting-House in a city." The French word dosme came to acquire the meaning of a cupola vault, specifically, by 1660. This French definition gradually became the standard usage of the English dome in the eighteenth century as many of the most impressive Houses of God were built with monumental domes, and in response to the scientific need for more technical terms.[2]

Characteristics[edit]

Comparison of a generic "true" arch (left) and a corbel arch (right).

A dome is a rounded vault made of either curved segments or a shell of revolution, meaning an arch rotated around its central vertical axis.[3] Domes can be made much thinner than corresponding arches of the same span. For example, a hemispherical dome can be 2.5 times thinner than a semicircular arch, and a dome with the profile of an equilateral arch can be thinner still.[4] Unlike voussoir arches, which require support for each element until the keystone is in place, domes are stable during construction as each level is made a complete and self-supporting ring.[5] Corbel domes achieve their shape by extending each horizontal layer of stones inward slightly farther than the previous, lower, one until they meet at the top. These are sometimes called false domes. True, or real, domes are formed with increasingly inward-angled layers of voussoirs which have ultimately turned 90 degrees from the base of the dome to the top.

A compound dome (red) with pendentives (yellow) from a sphere of greater radius than the dome.

A masonry dome produces thrusts down and outward. Thought of in terms of two kinds of forces at right angles from one another, meridional forces (like the meridians, or lines of longitude, on a globe) are compressive only, and increase towards the base, while hoop forces (like the lines of latitude on a globe) are in compression at the top and tension at the base, with the transition in a hemispherical dome occurring at an angle of 51.8 degrees from the top.[6] The optimal shape for a masonry dome of equal thickness is a catenary curve, similar to the curve of a parabola. This shape provides for perfect compression, without any of the tension or bending forces against which masonry is weak. Grounded hemispherical domes, by contrast, generate significant horizontal thrusts at their haunches.[7] The "haunch" is the part of an arch that lies roughly halfway between the base and the top.[8] These thrusts can be counteracted in masonry domes with the use of chains incorporated around the circumference or with external buttressing, although cracking along the meridians is still common.[6]

When the base of the dome does not match the plan of the supporting walls beneath it (for example, a circular dome on a square base), techniques are employed to transition between the two.[9] A variety of these techniques use what are called "squinches".[10] The simplest technique is to use diagonal lintels across the corners of the walls to create an octagonal base. Another is to use arches to span the corners, which can support more weight.[11] A squinch can be a single arch or a set of multiple projecting nested arches placed diagonally over an internal corner.[12] Squinches can take a variety of other forms, as well, including trumpet arches and niche heads, or half-domes.[10] The invention of pendentives superseded the squinch technique.[11] Pendentives are triangular sections of a sphere, like concave spandrels between arches, and are used to transition from the corners of a square bay to the circular base of a dome. The curvature of the pendentives is that of a sphere with a diameter equal to the diagonal of the square bay.[13] The precise definition of "pendentive" has been a source of contention among academics, including whether or not corbelling is permitted under the definition and whether or not the lower portions of a sail vault should be considered pendentives.[14]

Domes can be divided into two kinds: simple and compound, depending on the use of pendentives.[15] In the case of the simple dome, the pendentives are part of the same sphere as the dome itself; however, such domes are rare.[16] In the case of the more common compound dome, the pendentives are part of the surface of a larger sphere below that of the dome itself and form a circular base for either the dome or a drum section.[15] Drums, also called tholobates or tambours, are cylindrical or polygonal walls supporting a dome which may contain windows.

Because domes are concave from below, they can reflect sound and create echoes.[17] The half-domes over the apses of Byzantine churches, for example, helped to project the chants of the clergy.[18] Although this can compliment music, it may make speech less intelligible, leading Francesco Giorgi in 1535 to recommend vaulted ceilings for the choir areas of a church, but a flat ceiling filled with as many coffers as possible for where preaching would occur.[19] Cavities in the form of jars built into the inner surface of a dome may serve to compensate for this interference by diffusing sound in all directions, eliminating echoes while creating a "divine effect in the atmosphere of worship." This technique was written about by Vitruvius in his Ten Books on Architecture, which describes bronze and earthenware resonators.[17] The material, shape, contents, and placement of these cavity resonators determine the effect they have: reinforcing certain frequencies or absorbing them.[20]

Domes have been constructed from a wide variety of building materials over the centuries: from mud to stone, wood, brick, concrete, metal, glass and plastic.

The earliest domes in the Middle East were built with mud-brick and, eventually, with baked brick and stone. Domes of wood allowed for wide spans due to the relatively light and flexible nature of the material and were the normal method for domed churches by the 7th century, although most domes were built with the other less flexible materials. Wooden domes were protected from the weather by roofing, such as copper or lead sheeting.[21] Brick domes were the favored choice for large-space monumental coverings until the Industrial Age, due to their convenience and dependability.[22] The new building materials of the 19th century and a better understanding of the forces within structures from the 20th century has opened up new possibilities. Iron and steel beams, steel cables, and pre-stressed concrete have eliminated the need for external buttressing and enabled far thinner domes. Whereas earlier masonry domes may have had a radius to thickness ratio of 50, the ratio for modern domes can be in excess of 800. The lighter weight of these domes has not only permitted far greater spans, but also allowed for the creation of large movable domes over modern sports stadiums.[23]

History[edit]

Early history and primitive domes[edit]

Apache wigwam, by Edward S. Curtis, 1903

Cultures from pre-history to modern times constructed domed dwellings using local materials. Although it is not known when the first dome was created, sporadic examples of early domed structures have been discovered.

The earliest discovered may be four small dwellings made of Mammoth tusks and bones. The first was found by a farmer in Mezhirich, Ukraine, in 1965 while he was digging in his cellar and archaeologists unearthed three more.[24] They date from 19,280 - 11,700 BC.[25]

In modern times, the creation of relatively simple dome-like structures has been documented among various indigenous peoples around the world. The Wigwam was made by Native Americans using arched branches or poles covered with grass or hides. The Efé people of central Africa construct similar structures, using leaves as shingles.[26] Another example is the Igloo, a shelter built from blocks of compact snow and used by the Inuit people, among others. The Himba people of Namibia construct "desert igloos" of wattle and daub for use as temporary shelters at seasonal cattle camps, and as permanent homes by the poor.[27] Extraordinarily thin domes of sun-baked clay 20 feet in diameter, 30 feet high, and nearly parabolic in curve, are known from Cameroon.[28]

Drawing of an Assyrian bas-relief from Nimrud showing domed structures

The historical development from structures like these to more sophisticated domes is not well documented. That the dome was known to early Mesopotamia may explain the existence of domes in both China and the West in the first millennium BC.[29] Another explanation, however, is that the use of the dome shape in construction did not have a single point of origin and was common in virtually all cultures long before domes were constructed with enduring materials.[30]

Small domes in corbelled stone or brick over round-plan houses go back to the Neolithic period in the ancient Near East, and served as dwellings for poorer people throughout the prehistoric period, but domes did not play an important role in monumental architecture.[31] The discoveries of seal impressions in the ancient site of Chogha Mish (c. 6800 to 3000 BC), located in the Susiana plains of Iran, show the extensive use of dome structures in mud-brick and adobe buildings, likely granaries.[32] Other examples of mud-brick buildings that also seemed to employ the "true" dome technique have been excavated at Tell Arpachiyah, a Mesopotamian site of the Halaf (c. 6100 to 5400 BC) and Ubaid (ca. 5300 to 4000 BC) cultures.[33] Excavations at Tell al-Rimah have revealed pitched-brick domical vaults from about 2000 BC.[34] At the Sumerian Royal Cemetery of Ur, a "complete rubble dome built over a timber centring" was found among the chambers of the tombs for Meskalamdug and Puabi, dating to around 2500 BC.[35] Set in mud mortar, it was a "true dome with pendentives rounding off the angles of the square chamber." Other small domes can be inferred from the remaining ground plans, such as one in the courtyard of Ur-Nammu's ziggurat, and in later shrines and temples of the 14th century BC.[36] Some monumental Mesopotamian buildings of the Kassite period are thought to have had brick domes, but the issue is unsettled due to insufficient evidence in what has survived of these structures.[31]

A Neo-Assyrian bas-relief from Kuyunjik depicts domed buildings, although remains of such a structure in that ancient city have yet to be identified, perhaps due to the impermanent nature of sun-dried mudbrick construction.[37][38] However, because the relief depicts the Assyrian overland transport of a carved stone statue, the background buildings most likely refer to a foreign village, such as those at the foothills of the Lebanese mountains. The relief dates to the 8th century BC, while the use of domical structures in the Syrian region may go back as far as the fourth millennium BC.[39] Likewise, domed houses at Shulaveri in Georgia and Khirokitia, Cyprus, date back to around 6000 BC. The existing examples of beehive domes at Harran, Turkey, have been dated to the 19th century, and are similar to the trullos of Italy.[40]

Ancient stone corbelled domes have been found from the Middle East to Western Europe. Corbelled beehive domes were used as granaries in Ancient Egypt from the first dynasty, in mastaba tombs of the Old Kingdom, as pressure-relieving devices in private brick pyramids of the New Kingdom, and as kilns and cellars. They have been found in brick and in stone.[41] The mastaba tombs of Seneb and of Neferi are examples.[31] A model of a 10th dynasty house has also been found in Rifeh showing the tops of three domes just emerging through the terraced roof.[42] In an area straddling the borders between Oman, UAE, and Bahrain, stone beehive tombs built above ground called "Hafeet graves", or "Mezyat graves", date to the Bronze Age period between 3200 and 2700 BC.[43][44] Similar above-ground tombs made of corbelled stone domes have been found in the fourth cataract region of Nubia with dates beginning in the second millennium BC.[45] Examples on the Mediterranean island of Sardinia have been dated to 2500 BC. The so-called Treasury of Atreus, a large Mycenaean tomb covered with a mound of earth, dates to around 1330 BC.[46] It is about 15 meters in diameter and one of several tholos tombs with corbelled domes.[47] Some of the oldest traces of corbelled dome construction in the Iberian Peninsula can be found in the Province of Almería.[48]

Wooden domes were evidently used in Etruria on the Italian peninsula from archaic times. Reproductions were preserved as rock-cut Etruscan tombs produced until the Roman Imperial period, and paintings at Pompeii show examples of them in the third style and later.[49] Wooden domes may also have been used in ancient Greece, over buildings such as the Tholos of Epidaurus, which is typically depicted with a shallow conical roof.[50] Evidence for such wooden domes over round buildings in Ancient Greece, if they existed, has not survived and the issue is much debated.[51]

Although they had palaces of brick and stone, the kings of Achaemenid Persia held audiences and festivals in domical tents derived from the nomadic traditions of central Asia. They were likely similar to the later tents of the Mongol Khans. Called "Heavens", these tents emphasized the cosmic significance of the divine ruler. They were adopted by Alexander the Great after his conquest of the empire, and the domed baldachin of Roman and Byzantine practice was presumably inspired by this association.[52]

The possible use of domed ceilings in the architecture of Ptolemaic Egypt is suggested by rock-cut tombs in Alexandria, and by a poem from a third century BC papyrus that references a fountain niche covered with a semi-dome.[53] The earliest evidence of a Hellenistic dome is at the North Baths of Morgantina in Sicily, dated to the mid third century BC. The dome measured 5.75 metres in diameter over the circular hot room of the baths. It was made of terracotta tubes partially inserted into each other and arranged in parallel arches that were then completely covered with mortar. It is also the earliest known example of this technique of tubular vault construction. A Hellenistic bathing complex in nearby Syracuse may also have used domes like these to cover its circular rooms. Another dome with the same parallel arch construction but more refined technique has been identified in the tepidarium at a Roman era bathing complex in Cabrera del Mar, Spain, and dated to the middle of the second century BC.[54]

A stone pendentive dome is known from a first century BC bath in Petra.[55]

In the Saar basin of the Germanic north of Europe, the domical shape was used in wooden construction over houses, tombs, temples, and city towers, and was translated into masonry construction only after the beginning of Roman rule.[50]

Roman and Byzantine domes[edit]

Painting by Giovanni Paolo Pannini of the Pantheon in Rome, Italy, after its conversion to a church.

Roman domes are found in baths, villas, palaces, and tombs. Oculi are common features.[56] They are customarily hemispherical in shape and partially or totally concealed on the exterior. In order to buttress the horizontal thrusts of a large hemispherical masonry dome, the supporting walls were built up beyond the base to at least the haunches of the dome and the dome was then also sometimes covered with a conical or polygonal roof.[57]

Roman baths played a leading role in the development of domed construction in general, and monumental domes in particular. Modest domes in baths dating from the 2nd and 1st centuries BC are seen in Pompeii, in the cold rooms of the Terme Stabiane and the Terme del Foro.[58][59] These domes are very conical in shape, like those of the Assyrian bas-relief.[42][60] According to Vitruvius, the temperature and humidity of domed warm rooms could be regulated by raising or lowering bronze discs located under the oculus.[61] Domes were particularly well suited to the hot rooms of baths circular in plan to facilitate even heating from the walls. However, the extensive use of domes did not occur before the 1st century AD.[62]

Varro's book on agriculture describes an aviary with a wooden dome decorated with the eight winds that is compared by analogy to the eight winds depicted on the Tower of the Winds, which was built in Athens at about the same time. This aviary with its wooden dome may represent a fully developed type. Wooden domes in general would have allowed for very wide spans. Their earlier use may have inspired the development and introduction of large stone domes of previously unprecedented size. Domes reached monumental size in the Roman Imperial period.[58] Complex wooden forms were also necessary for dome centering and support during construction, and they seem to have eventually become more efficient and standardized over time. Formwork was arranged either horizontally or radially, but there is not enough surviving evidence from the first and second centuries to say what was typical.[63]

Although imprints of the formwork itself have not survived, deformations of up to 22 centimeters from the ideal at the so-called "Temple of Mercury" in Baiae suggest a centering of eight radiating frames, with horizontal connectors supporting radial formwork for the shallow dome.[64] The "Temple of Mercury", actually a concrete bath hall dating from the age of Augustus (27 BC – 14 AD), is the first known large Roman dome. There are five openings in the dome: a circular oculus and four square skylights.[58] The dome has a span of 21.5 meters and is the largest known dome built before that of the Pantheon.[65] It is also the earliest preserved concrete dome.[63]

The mortar and aggregate of Roman concrete was built up in horizontal layers laid by hand against wooden form-work with the thickness of the layers determined by the length of the workday, rather than being poured into a mold as concrete is today. Roman concrete domes were thus built similarly to the earlier corbel domes of the Mediterranean region, although they have different structural characteristics.[66] The aggregate used by the Romans was often rubble, but lightweight aggregate in the upper levels served to reduce stresses.[67] The dry concrete mixtures used by the Romans were compacted with rams to eliminate voids, and added animal blood acted as a water reducer.[68]

While there are earlier examples in the Republican period and early Imperial period, the growth of domed construction increases under Emperor Nero and the Flavians in the 1st century AD, and during the 2nd century. The opulent palace architecture of the Emperor Nero (54-68 AD) marks an important development.[69] There is evidence of a dome in his Domus Transitoria at the intersection of two corridors, resting on four large piers, which may have had an oculus at the center. In Nero's Domus Aurea, or "Golden House", the walls of a large octagonal room transition to an octagonal domical vault, which then transitions to a dome with an oculus.[70] This is the earliest existing example of a dome in the city of Rome itself.[64] The Domus Aurea was built after 64 AD and the dome was over 13 meters in diameter.[71] This octagonal and semicircular dome is made of concrete and the oculus is made of brick. The radial walls of the surrounding rooms buttress the dome, allowing the octagonal walls directly beneath it to contain large openings under flat arches and for the room itself to be unusually well-lit.[72] Because there is no indication that mosaic or other facing material had ever been applied to the surface of the dome, it may have been hidden behind a tent-like fabric canopy like the pavilion tents of Hellenistic (and earlier Persian) rulers. The oculus is unusually large, more than two-fifths the span of the room, and it may have served to support a lightweight lantern structure or tholos which would have covered the opening. Circular channels on the upper surface of the oculus also support the idea that this lantern, perhaps itself domed, was the rotating dome referred to in written accounts.[73] According to Suetonius, the Domus Aurea had a dome that perpetually rotated on its base in imitation of the sky.[74] It was reported in 2009 that newly discovered foundations of a round room may be those of the rotating domed dining hall.[75] Also reported in contemporary sources is a ceiling over a dining hall in the palace fitted with pipes so that perfume could rain from the ceiling, although it is not known whether this was a feature of the same dome.[76] The expensive and lavish decoration of the palace caused such scandal that it was abandoned soon after Nero's death and public buildings such as the Baths of Titus and the Colosseum were built at the site.[77]

Domes become standard under the reign of Emperor Domitian, although the only intact example is a 16.1 meter wide dome in what may have been a nymphaeum at his villa at Albano, today the church of Santa Maria della Rotunda.[71] Domitian's 92 AD Domus Augustana established the apsidal semi-dome as an imperial motif.[47] His palace contained three domes, each of which rested over walls with alternating apses and rectangular openings.[78] The dining hall of this private palace, called the Coenatio Jovis, or Dining Hall of Jupiter, contained a rotating ceiling like the one Nero had built, but with stars set into the simulated sky.[79] The audience halls of many Imperial palaces were domed.[47] Domes were also very common over polygonal garden pavilions.[80]

During the reign of Emperor Trajan, domes and semi-domes over exedras were standard elements of Roman architecture, possibly due to the efforts of Apollodorus of Damascus. Two rotundas 20 meters in diameter were finished in 109 AD as part of the baths built over the Domus Aurea, and exedras 13 and 18 meters wide were built as part of the markets north-east of his forum. The architecture of Trajan's successor, Hadrian, continued this style.[71] Although considered an example of Hadrianic architecture, there is brickstamp evidence that the rebuilding of the Pantheon in its present form was begun under Trajan.[77] Speculation that the architect of the Pantheon was Apollodorus has not been proven, although there are stylistic commonalities between his large coffered half-domes at Trajan's Baths and the dome of the Pantheon.[81]

The Pantheon, a temple in Rome completed by Emperor Hadrian as part of the Baths of Agrippa, is the most famous, best preserved, and largest Roman dome.[82] Dating from the 2nd century, it is an unreinforced concrete dome 43.4 meters wide resting on a circular wall, or rotunda, 6 meters thick. This rotunda, made of brick-faced concrete, contains a large number of relieving arches and is not solid. Seven interior niches and the entrance way divide the wall structurally into eight virtually independent piers. These openings and additional voids account for a quarter of the rotunda wall's volume. The only opening in the dome is the brick-lined oculus at the top, nine meters in diameter, that provides light and ventilation for the interior. The shallow coffering in the dome accounts for a less than five percent reduction in the dome's mass, and is mostly decorative. The aggregate material hand-placed in the concrete is heaviest at the base of the dome and changes to lighter materials as the height increases, dramatically reducing the stresses in the finished structure. In fact, many commentators cite the Pantheon as an example of the revolutionary possibilities for monolithic architecture provided by the use of Roman pozzolana concrete. However, vertical cracks seem to have developed very early, such that in practice the dome acts as an array of arches with a common keystone, rather than as a single unit. The exterior step-rings used to compress the "haunches" of the dome, which would not be necessary if the dome acted as a monolithic structure, may be an acknowledgement of this by the builders themselves. Such buttressing was common in Roman arch construction.[83] The roof was originally covered with gilt bronze tiles, but these were replaced by lead roofing in 663.[60] Hadrian is believed to have held court in the Pantheon rotunda using the main apse opposite the entrance as a tribune, which may explain its very large size.[81] It was more than twice as large as any known earlier dome.[84] No other dome built in the Imperial era came close to the span of the dome of the Pantheon.[85] It remained the largest dome in the world for more than a millennium and is still the world's largest unreinforced concrete dome.[86]

Segmented domes, made of radially concave wedges or of alternating concave and flat wedges, also appear under Hadrian in the 2nd century and most preserved examples of this style date from this period. Hadrian's Villa has examples at the Piazza D'Oro and in the semidome of the Serapeum. Recorded details of the decoration of the segmented dome at the Piazza D'Oro suggests it was made to evoke a billowing tent, perhaps in imitation of the canopies used by Hellenistic kings. Other examples exist at the Hadrianic baths of Otricoli and the so-called "Temple of Venus" at Baiae. This style of dome required complex centering and radially-oriented formwork to create its tight curves, and the earliest surviving direct evidence of radial formwork is found at the caldarium of the Large Baths at Hadrian's villa.[87] Hadrian was an amateur architect and it was apparently domes of Hadrian's like these that Trajan's architect, Apollodorus of Damascus, derisively called "pumpkins" prior to Hadrian becoming emperor. According to Dio Cassius, the memory of this insult contributed to Hadrian as emperor having Apollodorus exiled and killed.[88]

In the middle of the 2nd century, some of the largest domes were built near present day Naples, as part of large bath complexes taking advantage of the volcanic hot springs in the area. At the bath complex at Baiae, there are remains of a collapsed dome spanning 26.3 meters, called the "Temple of Venus", and a larger half-collapsed dome spanning 29.5 meters called the "Temple of Diana". The dome of the "Temple of Diana", which may have been a nymphaeum as part of the bath complex, can be seen to have had an ogival section made of horizontal layers of mortared brick and capped with light tufa. It dates to the second half of the second century and is the third largest dome known from the Roman world. The second largest is the collapsed "Temple of Apollo" built nearby along the shore of Lake Avernus. The span cannot be precisely measured due to its ruined state, but it was more than 36 meters in diameter.[71]

In the second half of the 2nd century in North Africa, a distinctive type of nozzle tube shape was developed in the tradition of the terracotta tube dome at the Hellenistic era baths of Morgantina, an idea that had been preserved in the use of interlocking terracotta pots for kiln roofs. This tube could be mass-produced on potter's wheels and interlocked together to form a permanent centering for concrete domes, avoiding the use of wooden centering altogether. This spread mainly in the western Mediterranean.[89]

In the 3rd century, Imperial mausolea began to be built as domed rotundas rather than tumulus structures or other types, following similar monuments by private citizens. Pagan and Christian domed mausolea from this time can be differentiated in that the structures of the buildings also reflect their religious functions. The pagan buildings are typically two story, dimly lit, free-standing structures with a lower crypt area for the remains and an upper area for devotional sacrifice. Christian domed mausolea contain a single well-lit space and are usually attached to a church.[90] Examples from the 3rd century include the brick domes of the Mausoleum of Galerius and the Mausoleum of Diocletian, and the mausoleum at Tor de' Schiavi.[91] The Mausoleum of Diocletian uses small arched squinches of brick built up from a circular base in an overlapping scales pattern, called a "stepped squinches dome". The scales pattern was a popular Hellenistic motif adopted by the Parthians and Sassanians, and such domes are likely related to Persian "squinch vaults".[92] Masonry domes were less common in the Roman provinces, although the 3rd century "Temple of Venus" at Baalbek was built with a stone dome 10 meters in diameter.[80] The large rotunda of the Baths of Agrippa, the oldest public baths in Rome, has been dated to the Severan period at the beginning of the third century, but it is not known whether this is an addition or simply a reconstruction of an earlier domed rotunda.[71] The technique of building lightweight domes with interlocking hollow ceramic tubes further developed in North Africa and Italy in the late third and early fourth centuries.[93] By the fourth century, the thin and lightweight tubed vaulting had become a vaulting technique in its own right, rather than simply serving as a permanent centering for concrete. It was used in early Christian buildings in Italy.[94] The later dome of the Baptistry of Neon in Ravenna is an example.[93]

In the 4th century, Roman domes proliferated due to changes in the way domes were constructed, including advances in centering techniques and the use of brick ribbing. The so-called "Temple of Minerva Medica", for example, used brick ribs along with step-rings and lightweight pumice aggregate concrete to form a decagonal dome.[95] The material of choice in construction gradually transitioned during the 4th and 5th centuries from stone or concrete to lighter brick in thin shells.[96] The use of ribs stiffened the structure, allowing domes to be thinner with less massive supporting walls. Windows were often used in these walls and replaced the oculus as a source of light, although buttressing was sometimes necessary to compensate for large openings. The Mausoleum of Santa Costanza has windows beneath the dome and nothing but paired columns beneath that, using a surrounding barrel vault to buttress the structure.[97] The largest centrally planned Early Christian church, Milan's domed San Lorenzo Maggiore, was built in the middle of the fourth century while that city served as the capital of the Western Empire.[98] There are two theories about the shape of this dome: a Byzantine-style dome on spherical pendentives with a ring of windows similar to domes of the later Justinian era, or an octagonal cloister vault following Roman trends and like the vaulting over the site's contemporary chapel of Saint Aquiline, possibly built with vaulting tubes, pieces of which had been found in excavations. Although these tubes have been shown to date from a medieval reconstruction, other evidence supports the latter theory in the use of Roman concrete in the original dome.[99] The original vaulting was concealed by a square drum externally rather than the octagon of today, which dates from the 16th century.[100]

Christian mausolea and shrines developed into the "centralized church" type, often with a dome over a raised central space.[101] The Church of the Holy Sepulchre in Jerusalem, for example, was likely built with a wooden dome over the shrine by the end of the 4th century.[102] The dome covered a rotunda, centered on the tomb of Christ, 33.7 meters in diameter and may have had an oculus.[103] The octagonal "Domus Aurea", or "Golden Octagon", built in 327 at the imperial palace of Antioch likewise had a domical roof, presumably of wood and covered with gilded lead.[104] The Church of the Holy Apostles, or Apostoleion, probably planned by Constantine but built by his successor Constantius in the new capital city of Constantinople, combined the congregational basilica with the centralized shrine. With a similar plan to that of the Church of Saint Simeon Stylites, four naves projected from a central rotunda containing Constantine's tomb and spaces for the tombs of the twelve Apostles.[105] Above the center may have been a clerestory with a wooden dome roofed with bronze sheeting and gold accents.[106] Centralized buildings of circular or octagonal plan also became used for baptistries and reliquaries due to the suitability of those shapes for assembly around a single object.[101] Baptisteries began to be built in the manner of domed mausolea during the 4th century in Italy. The octagonal Lateran baptistery or the baptistery of the Holy Sepulchre may have been the first, and the style spread during the 5th century.[107]

By the 5th century, structures with small-scale domed cross plans existed across the Christian world. Examples include the Mausoleum of Galla Placidia, the martyrium attached to the Basilica of San Simpliciano, and churches in Macedonia and on the coast of Asia Minor.[108] With the end of the Western Roman Empire, domes became a signature feature of the church architecture of the surviving Eastern Roman — or "Byzantine" — Empire.[109] Although rarely used, the pendentive dome was known in 2nd century Roman architecture, such as the funerary monuments of the Sedia dei Diavolo and the Torracio della Secchina on the Via Nomentana, but would be used much more widely in the Byzantine period.[71]

Early examples of Byzantine domes existed over the hexagonal hall of the Palace of Antiochos, the hexagon at Gülhane, the martyium of Sts. Karpos and Papylos, and the rotunda at the Myrelaion.[110] The Church of Saint Simeon Stylites likely had a wooden polygonal dome over its central 27 meter wide octagon.[111] The square bay with an overhead sail vault or dome on pendentives became the basic unit of architecture in the early Byzantine centuries, found in a variety of combinations.[108] Underground cisterns in Constantinople, such as the Cistern of Philoxenos and the Basilica Cistern, were composed of a grid of columns supporting small domes, rather than groin vaults.[109] Small brick domes are also found in towers of Constantinople's early fifth century land walls.[110]

The first known domed basilica may have been a church at Meriamlik in southern Turkey, dated from 471–494, although the ruins do not provide a definitive answer. It is possible earlier examples existed in Constantinople, where it has been suggested that the plan for the Meriamlik church itself was designed, but no domed basilica has been found there before the 6th century. The Church of St. Polyeuctus in Constantinople (524–527) was apparently built as a large and lavish domed basilica similar to the Meriamlik church of fifty years before and to the later Hagia Irene of Emperor Justinian, by Anicia Juliana, a descendent of the former Imperial House.[112] The church included an inscription praising Juliana for having "surpassed Solomon" with the building, and it may have been with this in mind that Justinian would later say of his Hagia Sophia, "Solomon, I have vanquished thee!".[113][114]

The dome of Hagia Sophia, or Church of the Holy Wisdom, in Istanbul, Turkey

6th-century church building by the Emperor Justinian used the domed cross unit on a monumental scale, in keeping with Justinian's emphasis on bold architectural innovation. His church architecture emphasized the central dome. Centrally planned domed churches had been built since the 4th century for very particular functions, such as palace churches or martyria, with a slight widening of use around 500 AD, but Justinian's architects make the domed brick-vaulted central plan standard throughout the Roman east. This divergence with the Roman west from the second third of the 6th century may be considered the beginning of a "Byzantine" architecture.[115]

The earliest existing of Justinian's domed buildings is the central plan Church of Saints Sergius and Bacchus in Constantinople, completed by 536. The dome rests on an octagonal base created by eight arches on piers and is divided into sixteen sections. Those sections above the flat sides of the octagon are flat and contain a window at their base, alternating with sections from the corners of the octagon that are scalloped, creating an unusual kind of pumpkin dome.[116]

After the Nika Revolt destroyed much of the city of Constantinople in 532, Justinian had the opportunity to rebuild. Both the churches of Hagia Irene ("Holy Peace") and Hagia Sophia ("Holy Wisdom") were burned down. Both had been basilica plan churches and both were rebuilt as domed basilicas, although the Hagia Sophia was rebuilt on a much grander scale.[117]

Built by Anthemius of Tralles and Isidore of Miletus in Constantinople between 532 and 537, the Hagia Sophia has been called the greatest building in the world. It is an original and innovative design with no known precedents in the way it covers a basilica plan with dome and semi-domes. Periodic earthquakes in the region have caused three partial collapses of the dome and necessitated repairs. The precise shape of the original central dome completed in 537 was significantly different from the current one and, according to contemporary accounts, much bolder. Procopius wrote that the dome seemed "not to rest upon solid masonry, but to cover the space with its golden dome suspended from heaven." Byzantine chronicler John Malalas reported that the original dome was 20 byzantine feet lower than its replacement. One theory is that the original dome continued the curve of the pendentives, creating a massive sail vault pierced with a ring of windows. A more recent theory raises the shallow cap of this dome (the portion above what are today the pendentives) on a relatively short recessed drum containing the windows, which was mentioned by Procopius. This first dome partially collapsed due to an earthquake in 558 and the design was then revised to the present profile. Earthquakes also caused partial collapses of the dome in 989 and 1346. The current central dome is about 32 meters wide. It contains 40 radial ribs that spring from between 40 windows at the base of the dome. The dome and pendentives are supported by four large arches springing from four piers. Additionally, two huge semi-domes of similar proportion are placed on opposite sides of the central dome, which themselves contain smaller semi-domes between an additional four piers.[118] The brick dome also incorporated a wooden tension ring at its base to resist outward thrust and interrupt cracking, and iron cramps between the marble blocks of its cornice.[119] It is about 750 millimeters thick.[3]

The octagonal Basilica of San Vitale in Ravenna, Italy, was completed in 547 and contains a terracotta dome.[120] Hollow amphorae were fitted inside one another to provide a lightweight structure and avoid additional buttressing.[121] It is 18 meters in diameter.[80] The amphorae were arranged in a continuous spiral, which required minimal centering and formwork but was not strong enough for large spans.[91] The dome was covered with a timber roof, which would be the favored practice for later medieval architects in Italy although it was unusual at the time.[121] Justinian's church dome at Qasr ibn Wardan is also unusual in that the pendentives sprang from an octagonal drum, rather than the four main arches, and in that it was made of brick, which was rare in Syria.[110]

Justinian also tore down the aging Church of the Holy Apostles and rebuilt it on a grander scale between 536 and 550.[122] The original building was a cruciform basilica with a central domed mausoleum. Justinian's replacement was apparently likewise cruciform but with a central dome and four flanking domes. The central dome over the crossing had pendentives and windows in its base, while the four domes over the arms of the cross had pendentives but no windows.[123] The domes appear to have been radically altered between 944 and 985 by the addition of windowed drums beneath all five domes and by raising the central dome higher than the others.[124] Justinian's Basilica of St. John at Ephesus and Venice's St Mark's Basilica are derivative of Holy Apostles.[123] More loosely, the Cathedral of St. Front and the Basilica of Saint Anthony of Padua are also derived from this church.[125]

The seventh to ninth centuries, roughly corresponding to the period of Iconoclasm, are poorly documented but can be considered a transitional period.[126] With the decline in the empire's resources following losses in population and territory, domes in Byzantine architecture were used as part of more modest new buildings. The large-scale churches of Byzantium were, however, kept in good repair. The upper portion of the Church of Hagia Irene was thoroughly rebuilt after an earthquake in 740. The nave was re-covered with an elliptical domical vault hidden externally by a low cylinder on the roof, in place of the earlier barrel vaulted ceiling, and the original central dome from the Justinian era was replaced with one raised upon a high windowed drum. The barrel vaults supporting these two new domes were also extended out over the side aisles, creating cross-domed units.[122] These units became a standard element on a smaller scale in later Byzantine church architecture.[127] By bracing the dome with broad arches on all four sides, the cross-domed unit provided a more secure structural system.[126]

The Nea Ekklesia of Emperor Basil I was built in Constantinople around 880 as part of a substantial building renovation and construction program during his reign. It had five domes, which are known from literary sources, but different arrangements for them have been proposed under at least four different plans. One has the domes arranged in a cruciform pattern like those of the contemporaneous Church of St. Andrew at Peristerai or the much older Church of the Holy Apostles in Constantinople. Others arrange them in a quincunx pattern, with four minor domes in the corners of a square and a larger fifth in the center, as part of a cross-domed or cross-in-square plan.[128] It is often suggested that the five-domed design of St. Panteleimon at Nerezi, from 1164, is based on that of the Nea Ekklesia.[129]

The Church of St. Panteleimon, Nerezi, Macedonia has five domes in a quincunx pattern.

The Cross-in-square plan, with a single dome at the crossing or five domes in a quincunx pattern, became widely popular in the Middle Byzantine period (c. 843-1204).[130][131][126] Examples include an early 9th century church in Tirilye, now called the Fatih Mosque, and a palace chapel built around 920, called the Myrelaion.[132] It is the most common church plan from the tenth century until the fall of Constantinople in 1453.[133] This type of plan, with four columns supporting the dome at the crossing, was best suited for domes less than 7 meters wide and, from the tenth to the 14th centuries, a typical Byzantine dome measured less than 6 meters in diameter. For domes beyond that width, variations in the plan were required such as using piers in place of the columns and incorporating further buttressing around the core of the building.[134] In this period, domes were normally built to emphasize separate functional spaces, rather than as the modular ceiling units they had been earlier.[135] Resting domes on circular or polygonal drums pierced with windows eventually became the standard style, with regional characteristics.[136] The distinctive rippling eaves design for the roofs of domes also begins in the 10th century. In mainland Greece, circular or octagonal drums became the most common while, in Constantinople, drums with twelve or fourteen sides were popular beginning in the 11th century.[136] The 11th century rock-cut churches of Cappadocia, such as Karanlik Kilise and Elmali Kilise in Göreme, have shallow domes without drums due to the dim natural lighting of cave interiors.[137]

The domed-octagon plan is a variant of the cross-in-square plan.[131] The earliest extant example is the katholikon at the monastery of Hosios Loukas, with a 9 meter wide dome built in the first half of the 11th century.[122] This hemispherical dome was supported by a sophisticated and open structural system, with the weight of the dome distributed on eight piers, rather than four, and corbelling used to avoid concentrating weight on their corners. The use of squinches to transition from those eight supports to the base of the dome has led to speculation of a design origin in Arab, Sasanian, or Caucasian architecture, although with a Byzantine interpretation.[138] The smaller monastic church at Daphni, c. 1080, uses a simpler version of this plan.[139] The katholikon of Nea Moni, a monastery on the island of Chios, was built some time between 1042 and 1055 and featured a nine sided, ribbed dome rising 15.62 meters above the floor (this collapsed in 1881 and was replaced with the slightly taller present version). The transition from the square naos to the round base of the drum is accomplished by eight conches, with those above the flat sides of the naos being relatively shallow and those in the corners of the being relatively narrow. The novelty of this technique in Byzantine architecture has led to it being dubbed the "island octagon" type, in contrast to the "mainland octagon" type of Hosios Loukas. Speculation on design influences have ranged from Arab influence transmitted via the recently built domed octagon chapels at the Church of the Holy Sepulchre in Jerusalem or the Al-Hakim Mosque in Islamic Cairo, to Caucasian buildings such as the Armenian Cathedral of the Holy Cross. Later copies of the Nea Moni, with alterations, include the churches of Agios Georgios Sykousis, Agioi Apostoli at Pyrghi, Panagia Krina, and the Church of the Metamorphosis in Chortiatis.[140] There is a written account by Nicholas Mesarites of a Persian-style muqarnas dome built as part of a late 12th century Imperial palace in Constantinople.[141]

Another variant of the cross-in-square, the "so-called atrophied Greek cross plan", also provides greater support for a dome than the typical cross-in-square plan by using four piers projecting from the corners of an otherwise square naos, rather than four relatively slender columns. This design was used in the Chora Church of Constantinople in the twelfth century after the previous cross-in-square structure was destroyed by an earthquake.[142] The twelfth century Pantokrator monastic complex (1118–36) was built with imperial sponsorship as three adjoining churches.[143]

The Late Byzantine Period, from 1204 to 1453, has an unsettled chronology of buildings, especially during the Latin Occupation. The fragmentation of the empire, beginning in 1204, is reflected in a fragmentation of church design and regional innovations. After 1261, new church architecture in Constantinople consisted mainly of additions to existing monastic churches, such as the Monastery of Lips and Pammakaristos Church, and as a result the building complexes are distinguished in part by an asymmetric array of domes on their roofs. This effect may have been in imitation of the earlier triple church Pantokrator monastic complex.[144] A 15th century account of a Russian traveler to Constantinople mentions an abandoned hall, presumably domed, "in which the sun, the moon, and the stars succeeded each other as in heaven."[141]

In the Despotate of Epirus, the Church of the Parigoritissa (1282-9) is the most complex example, with a domed octagon core. In Mistra, there are several basilica plan churches with cross-in-square, five-domed galleries. The Aphentiko at Brontochion Monastery was built c. 1310-22 and the later church of the Pantanassa Monastery (1428) is of the same type.[145]

In Thessaloniki, a distinctive type of church dome developed in the first two decades of the fourteenth century. It is characterized by a polygonal drum with rounded colonnettes at the corners, all brick construction, and faces featuring three arches stepped back within one another around a narrow "single-light window".[146] One of the hallmarks of Thessalonian churches was the plan of a domed naos with a peristoon wrapped around three sides.[147] The churches of Hagios Panteleimon, Hagia Aikaterine, and Hagioi Apostoloi have domes on these ambulatory porticoes.[145] The five domes of the Church of the Holy Apostles in Thessaloniki (c. 1329) makes it an example of a five-domed cross-in-square church in the Late Byzantine style, as is the Gračanica monastery, built around 1311 in Serbia.[133] The architect and artisans of the Gračanica monastery church probably came from Thessaloniki and its style reflects Byzantine cultural influence.[148] The church has been said to represent "the culmination of Late Byzantine architectural design."[145]

Byzantium's neighboring Orthodox powers emerge as architectural centers in their own right during this period. The Bulgarian churches of Nesebar are similar to those in Constantinople at this time and, following the construction of Gračanica monastery, the architecture of Serbia used the "so-called Athonite plan", for example at Ravanica (1375-7). In Romania, Wallachia was influenced by Serbian architecture and Moldavia was more original, such as in the Voroneț Monastery with its small dome.[145] Moscow emerged as the most important center following the fall of Constantinople in 1453.[149]

The exact relationship between Byzantine architecture and that of the Caucasus is unclear. Georgia and Armenia produced many central planned, domed buildings in the seventh century, experienced a hiatus during the Arab invasions, and the architecture flourished again in the Middle Byzantine Period.[126] Armenian church domes were initially wooden structures. Etchmiadzin Cathedral (c. 483) originally had a wooden dome covered by a wooden pyramidal roof before this was replaced with stone construction in 618. Churches with stone domes became the standard type after the 7th century, perhaps benefiting from a possible exodus of stonecutters from Syria, but the long traditions of wooden construction carried over stylistically. Some examples in stone as late as the 12th century are detailed imitations of clearly wooden prototypes.[150]

Byzantine domes were normally hemispherical and had, with occasional exceptions, windowed drums. All of the surviving examples in Constantinople are ribbed or pumpkin domes, with the divisions corresponding to the number of windows. Aided by the small scale of churches after the sixth century, such ribbed domes could be built with formwork only for the ribs. Pumpkin domes could have been built in self-supporting rings and small domical vaults were effectively corbelled, dispensing with formwork altogether. Roofing for domes ranged from simple ceramic tile to more expensive, more durable, and more form-fitting lead sheeting. The domes and drums typically incorporated wooden tension rings at several levels within the structures to resist deformation in the mortar and allow for faster construction, a technique frequently said to be a later invention of Filippo Brunelleschi. Metal clamps between stone cornice blocks, metal tie rods, and metal chains were also used to stabilize domed construction.[137] Timber belts at the bases of domes help to stabilize the walls below them during earthquakes, but the domes themselves remain vulnerable to collapse.[151] The technique of using double shells for domes, although revived in the Renaissance, originated in Byzantine practice.[152]

Chinese domes[edit]

Model of the Lei Cheng Uk Han Tomb (25 AD – 220 AD).

Very little has survived of ancient Chinese architecture, due to the extensive use of timber as a building material. Brick and stone vaults used in tomb construction have survived, and the corbeled dome was used, rarely, in tombs and temples.[153] The earliest true domes found in Chinese tombs were shallow cloister vaults, called simian jieding, derived from the Han use of barrel vaulting. Unlike the cloister vaults of western Europe, the corners are rounded off as they rise.[154]

A model of a tomb found with a shallow true dome from the late Han Dynasty (206 BC – 220 AD) can be seen at the Guangzhou Museum (Canton).[155] Another, the Lei Cheng Uk Han Tomb, found in Hong Kong in 1955, has a design common among Eastern Han Dynasty (25 AD – 220 AD) tombs in South China: a barrel vaulted entrance leading to a domed front hall with barrel vaulted chambers branching from it in a cross shape. It is the only such tomb that has been found in Hong Kong and is exhibited as part of the Hong Kong Museum of History.[156][157]

During the Three Kingdoms period (220–280), the "cross-joint dome" (siyuxuanjinshi) was developed under the Wu and Western Jin dynasties south of the Yangtze River, with arcs building out from the corners of a square room until they met and joined at the center. These domes were stronger, had a steeped angle, and could cover larger areas than the relatively shallow cloister vaults. Over time, they were made taller and wider. There were also corbel vaults, called diese, although these are the weakest type.[158] Some tombs of the Song Dynasty (960–1279) have beehive domes.[155]

Persian domes[edit]

Main article: Gonbad
See also: Persian domes

Persian architecture likely inherited an architectural tradition of dome-building dating back to the earliest Mesopotamian domes.[38] Due to the scarcity of wood in many areas of the Iranian plateau, domes were an important part of vernacular architecture throughout Persian history.[159]

The remains of a large domed circular hall measuring 17 meters in diameter in the Parthian capital city of Nyssa has been dated to perhaps the first century AD. It "shows the existence of a monumental domical tradition in Central Asia that had hitherto been unknown and which seems to have preceded Roman Imperial monuments or at least to have grown independently from them."[160] It likely had a wooden dome.[161] The Sun Temple at Hatra appears to indicate a transition from columned halls with trabeated roofing to vaulted and domed construction in the first century AD, at least in Mesopotamia. The domed sanctuary hall of the temple was preceded by a barrel vaulted iwan, a combination that would be used by the subsequent Sasanian Empire.[162] An account of a Parthian domed palace hall from around 100 AD in the city of Babylon can be found in the Life of Apollonius of Tyana by Philostratus. The hall was used by the king for passing judgments and was decorated with a mosaic of blue stone to resemble the sky, with images of gods in gold.[163] A bulbous Parthian dome can be seen in the relief sculpture of the Arch of Septimius Severus in Rome, its shape apparently due to the use of a light tent-like framework.[164]

The Palace of Ardashir, constructed in AD 224. The building is composed of three large domes, among other structures.

The Persian invention of the squinch, a series of concentric arches forming a half-cone over the corner of a room, enabled the transition from the walls of a square chamber to an octagonal base for a dome. Previous transitions to a dome from a square chamber existed but were makeshift in quality and only attempted on a small scale, not being reliable enough for large constructions. The squinch enabled domes to be widely used and they move to the forefront of Persian architecture as a result.[165] The ruins of the Palace of Ardashir and Ghal'eh Dokhtar in Fars Province, Iran, built by Ardashir I (224–240) of the Sasanian Empire, have the earliest known examples.[159]

The three domes of the Palace of Ardashir are 45 feet in diameter and vertically elliptical, each with a central opening or oculus to admit light.[166] They were built with local stone and mortar and covered with plaster on the interior.[167] The large brick dome of the Sarvestan Palace, also in Fars but later in date, shows more elaborate decoration and four windows between the corner squinches. Also called "the Temple of Anahita", the building may have been a Fire temple.[167][159] Instead of using a central oculus in each dome, as at the Palace of Ardashir and as shown in the bas relief found at Kuyunjik, lighting was provided by a number of hollow terracotta cylinders set into the domes at regular intervals.[168] Multiple written accounts from Arabic, Byzantine, and Western medieval sources describe a palace domed structure over the throne of Chosroes decorated in blue and gold. The dome was covered with depictions of the sun, moon, stars, planets, the zodiac, astrapai, and kings, including Chosroes himself. According to Ado and others, the dome could produce rain, and could be rotated with a sound like thunder by means of ropes pulled by horses in a basement.[169] Caravansaries used the domed bay from the Sasanian period to the Qajar dynasty.[159]

Chahar-taqi, or "four vaults", were smaller Zoroastrian fire temple structures with four supports arranged in a square, connected by four arches, and covered by central ovoid domes. The Niasar Zoroastrian temple in Kashan and the chahar-taqi in Darreh Shahr are examples.[170] Such temples, square domed buildings with entrances at the axes, inspired the forms of early mosques after the Islamic conquest of the empire in the 7th century.[171] These domes are the most numerous surviving type from the Sasanian period, with some having been converted into mosques. The later isolated dome chambers called the "kiosk mosque" type may have developed from this.[159] Pre-Islamic domes in Persia are commonly semi-elliptical, with pointed domes and those with conical outer shells being the majority of the domes in the Islamic periods.[172]

Although the Sasanians did not create monumental tombs, the domed chahar-taqi may have served as memorials. A Soghdian painting fragment from the early eighth century found at Panjakent appears to depict a funerary dome (possibly a tent) and this, along with a few ossuaries of an architectural nature, indicates a possible tradition in central Asia of a funerary association with the domed form. The area of north-eastern Iran was, along with Egypt, one of two areas notable for early developments in Islamic domed mausoleums, which appear in the tenth century.[173]

Golden dome above the mausoleum of Fatima Masumah in Qom

The earliest known Islamic domes in Persia, such as the Great Mosque of Qom (878) and the tomb of Muhammed b. Musa (976), seem to have continued the rounded Sasanian form.[174] Domed mausoleums contributed greatly to the development and spread of the dome in Persia early in the Islamic period,. By the 10th century, domed tombs had been built for Abbasid caliphs and Shiite martyrs. Pilgrimage to these sites may have helped to spread the form.[159] The earliest surviving example, the Qubbat-al Sulaibiya, was an octagonal structure with a central dome on a drum built around 892 in Samarra.[175] The Samanid Mausoleum in Transoxiana dates to no later than 943 and is the first to have squinches create a regular octagon as a base for the dome, which then became the standard practice. The Arab-Ata Mausoleum, also in Transoxiana, may be dated to 977–78 and uses muqarnas between the squinches for a more unified transition to the dome. Cylindrical or polygonal plan tower tombs with conical roofs over domes also exist beginning in the 11th century.[159] The earliest example is the Gonbad-e Qabus tower tomb, 57 meters high and spanning 9.7 meters, which was built in 1007.[176][175]

The Seljuq Turks built tower tombs, called "Turkish Triangles", as well as cube mausoleums covered with a variety of dome forms. Seljuk domes included conical, semi-circular, and pointed shapes in one or two shells. Shallow semi-circular domes are mainly found from the Seljuk era. The double-shell domes were either discontinuous or continuous. The continuous double-shell domes separated from one another at an angle of 22.5 degrees from their base, such as the dome of the Friday mosque in Ardestan, whereas the discontinuous domes remained completely separate, such as those of the tower tombs of Kharrqan.[177] This pair of brick tower tombs from the 11th century in Kharraqan, Iran, are the earliest known masonry double shell domes. The domes may have been modeled on earlier wooden double shell domes, such as that of the Dome of the Rock. It is also possible, because the upper portions of both of the outer shells are missing, that some portion of the outer domes may have been wooden.[178] These brick mausoleum domes were built without the use of centering, a technique developed in Persia.[179] The Seljuq Empire introduced the domed enclosure in front of the mosque's mihrab, which would become popular in Persian congregational mosques. The domed enclosure of the Jameh Mosque of Isfahan, built in 1086-7 by Nizam al-Mulk, was the largest masonry dome in the Islamic world at that time, had eight ribs, and introduced a new form of corner squinch with two quarter domes supporting a short barrel vault. In 1088 Tāj-al-Molk, a rival of Nizam al-Mulk, built another dome at the opposite end of the same mosque with interlacing ribs forming five-pointed stars and pentagons. This is considered the landmark Seljuk dome, and may have inspired subsequent patterning and the domes of the Il-Khanate period. The use of tile and of plain or painted plaster to decorate dome interiors, rather than brick, increased under the Seljuks.[159] One of the largest Seljuq domes was that of the Jameh Mosque of Qazvin, built over the site of a Sassanian Fire Temple, which had a span of 15.2 meters.[180] The Tomb of Ahmed Sanjar had a large double shell, intersecting ribs over plain squinches, and the exterior was elaborately decorated at the zone of transition with arches and stucco work.[159] The tomb of Sultan Sanjar, who reigned from 1117 to 1157, was damaged in the sack of Merv in 1221 by Tolui Khan.[174]

After the disruptive effects of several Mongol invasions, Persian architecture again flourished in the Ilkhanate and Timurid periods. Characteristic of these domes are the use of high drums and several types of discontinuous double-shells, and the development of triple-shells and internal stiffeners occurred at this time. Beginning in the Ilkanate, Persian domes achieved their final configuration of structural supports, zone of transition, drum, and shells, and subsequent evolution was restricted to variations in form and shell geometry. The construction of tomb towers decreased.[181] The two major domes of the IlKhanate period are the no-longer-existing mausoleum of Ghazan in Tabriz and the Mausoleum of Öljaitü in Soltaniyeh, the latter having been built to rival the former.[159] Öljaitü was the first sovereign of Persia to declare himself of the Shia sect of Islam and built the mausoleum, with the largest dome in Persia, to house the bodies of Ali and Hussein as a pilgrimage site. This did not occur and it became his own mausoleum instead.[182] The dome measures 50 meters high and almost 25 meters in diameter and has the best surviving tile and stucco work from this period. The thin, double-shelled dome was reinforced by arches between the layers.[159] The tall proportions of the Jameh Mosque of Varamin resulted primarily from the increased height of the zone of transition, with the addition of a sixteen-sided section above the main zone of muqarnas squinches.[159] The 7.5 meter wide double dome of Soltan Bakht Agha Mausoleum (1351-1352) is the earliest known example in which the two shells of the dome have significantly different profiles, which spread rapidly throughout the region. The inner and outer shells had radial stiffeners and struts between them.[183]

At the Timurid capital of Samarkand, nobles and rulers in the 14th and 15th centuries began building tombs with double-shelled domes containing cylindrical masonry drums between the shells. In the Gur-e Amir, built by Timur around 1404, a timber framework on the inner dome supports the outer, bulbous dome. Radial tie-bars at the base of the bulbous dome provide additional structural support. Timber reinforcement rings and rings of stone linked by iron cramps were also used to compensate for the structural problems introduced by using such drums.[184] Radial sections of brick walls with wooden struts were used between the shells of discontinuous double domes to provide structural stability as late at the 14th century.[185] A miniature painted at Samarkand shows that bulbous cupolas were used to cover small wooden pavilions in Persia by the beginning of the fifteenth century. They gradually gained in popularity.[186] The large, bulbous, fluted domes on tall drums that are characteristic of 15th century Timurid architecture were the culmination of the Central Asian and Iranian tradition of tall domes with glazed tile coverings in blue and other colors.[21] The Sanctuary of Ahmed Yasawi, situated in southern Kazakhstan was never finished, but has the largest existing brick dome in Central Asia, measuring 18.2 m in diameter. The dome exterior is covered with hexagonal green glazed tiles with gold patterns.[187] The dome of the Amir Chakhmaq mosque (1437) has a semi-circular inner shell and an advanced system of stiffeners and wooden struts supporting a shallow pointed outer shell. Notably, the dome has a circular drum with two tiers. Another double shell dome from the early Seljuq period at the shrine complex of Bayazid Bastami was changed in the Timurid period by the addition of a third conical shell over the existing two domed shells. Triple-shelled domes are rare outside of the Timurid era.[188] The triple-shell dome of the madrasa of Goharshad is the first of its kind. The middle dome may have been added as reinforcement.[159]

The domes of the Safavid dynasty are characterized by a distinctive bulbous profile and are considered to be the last generation of Persian domes. They are generally thinner than earlier domes and are decorated with a variety of colored glazed tiles and complex vegetal patterns.[189] The palace of Ālī Qāpū includes small domed rooms decorated with artificial vegetation.[141] The oldest example is over the octagonal mausoleum of Khwaja Rabi (1617-1622). The outstanding example is the dome of the Masjid-e Shah, or Royal Mosque (1611-1638). The bulbous dome is a discontinuous double-shell 33 meters wide and 52 meters high. Safavid domes were influential on those of other Islamic styles, such as the Mughal architecture of India.[190]

In the Qajar period (1779-1924), the movement to modern architecture meant less innovation in dome construction. Domes were built over madrasas, such as the 1848 Imam madrasa, or Sultani school, of Kashan, but they have relatively simple appearances and do not use tiled mosaics.[190] The covered markets or bazaars (tīmcās) at Qom and Kashan feature a central dome with smaller domes on either side and elaborate muqarnas. An exaggerated style of onion dome on a short drum, as can be seen at the Shah Cheragh (1852-1853), first appeared in the Qajar period. Domes have remained important in modern mausoleums, such as the tombs of Ḥāfeẓ, Saʿdī, Reza Shah, and Ruhollah Khomeini in the twentieth century. Domed cisterns and icehouses remain common sights in the countryside.[159]

Persian domes from different historical eras can be distinguished by their transition tiers: the squinches, spandrels, or brackets that transition from the supporting structures to the circular base of a dome. Drums, after the Ilkanate era, tend to be very similar and have an average height of 30 to 35 meters from the ground. They are where windows are located. Inner shells are commonly semi-circular, semi-elliptical, pointed, or saucer shaped. The outer shell of a Persian dome reduces in thickness every 25 or 30 degrees from the base. Outer shells can be semi-circular, semi-elliptical, pointed, conical, or bulbous, and this outer shape is used to categorize them. Pointed domes can be sub-categorized as having shallow, medium, and sharp profiles, and bulbous domes as either shallow or sharp. Double domes use internal stiffeners with wooden struts between the shells, with the exception of those with conical outer shells. [191]

Arabic and Western-European domes[edit]

The Dome of the Rock in Jerusalem

Seventeen years after the last Western Roman Emperor was deposed, Theodoric the Great was the Ostrogothic king of Italy. His building projects largely continued existing architectural conventions. His Arian Baptistry in Ravenna (c. 500), for example, closely echoes the Baptistry of Neon built before it.[192] Both baptistries are octagonal buildings with pyramidal roofs concealing interior domes.

The Mausoleum of Theodoric, however, was understood by contemporaries to be remarkable.[192] Begun in 520, the 36-foot-wide (11 m) dome over the mausoleum was carved out of a single 440-ton slab of limestone and positioned some time between 522 and 526.[193] The low saucer shape of the monolithic dome, which is estimated to be more than 230 tons of Istrian stone, may have been chosen to avoid radial cracking.[110] The twelve brackets carved as part of the dome's exterior are thought to have been used to maneuver the piece into place. The choice of large limestone blocks for the structure is significant as the most common construction material in the West at that time was brick. It is likely that foreign artisans were brought to Ravenna to build the structure; possibly from Syria, where such stonework was used in contemporary buildings.[193]

The Syria and Palestine area has a long tradition of domical architecture, including wooden domes in shapes described as "conoid", or similar to pine cones. When the Arab Muslim forces conquered the region, they employed local craftsmen for their buildings and, by the end of the 7th century, the dome had begun to become an architectural symbol of Islam. The rapidity of this adoption was likely aided by the Arab religious traditions, which predate Islam, of both domed structures to cover the burial places of ancestors and the use of a round tabernacle tent with a dome-like top made of red leather for housing idols.[194] Early versions of bulbous domes can be seen in mosaic illustrations in Syria dating to the Umayyad period. They were used to cover large buildings in Syria after the eleventh century.[186]

The Dome of the Rock in Jerusalem, the earliest surviving Islamic building, was completed in 691 by Umayyad caliph Abd Al-Malik.[195] Its design was that of a ciborium, or reliquary, such as those common to Byzantine martyria and the major Christian churches of the city.[196] The dome, a double shell design made of wood, is 20.44 meters in diameter and 30 meters high.[197] The dome's bulbous shape "probably dates from the eleventh century."[186] Several restorations since 1958 to address structural damage have resulted in the extensive replacement of tiles, mosaics, ceilings, and walls such that "nearly everything that one sees in this marvelous building was put there in the second half of the twentieth century", but without significant change to its original form and structure. It is currently covered in gilded aluminum.[198]

In addition to religious shrines, domes were used over the audience and throne halls of Umayyad palaces, and as part of porches, pavilions, fountains, towers and the calderia of baths. Blending the architectural features of both the Byzantine and Persian architecture, the domes used both pendentives and squinches and were made in a variety of shapes and materials.[199] A dome stood at the center of the palace-city of Bahgdad and, similarly but on a smaller scale, there are literary accounts of a domed audience hall in the palace of Abu Muslim in Merv at the meeting point of four iwans arranged along the cardinal directions.[200][201] Muslim palaces included domical halls as early as the eighth century, well before domes became standard elements of mosque architecture. The early eighth century palace of Khirbat al-Minya included a domed gateway. The palace of Qasr Mshatta and a ninth century palace at Samarra included domed throne rooms. A domed structure covered a shallow pool in the main courtyard of the mid eighth century palace of Khirbat al-Mafjar. Similar examples at mosques, such as the domed fountains at the Mosque of Ibn Tulun (destroyed in 987 and replaced with a different structure), at Maarrat al-Numan, in Nishapur, Tripoli, and at the Mosque of Damascus seem to be related to this element of palace architecture, although they were later used as part of ritual ablution.[202] The calderia of early Islamic bath complexes at Amra, Sarraj, and Anjar were roofed with stone or brick domes.[199] The caldarium of the early Islamic bath at Qasr Amra contains "the most completely preserved astronomical cupola decoration", a decorative idea for bath domes that would long continue in the Islamic world.[203]

The placement of a dome in front of the mihrab of a mosque probably began with the rebuilding of the Prophet's Mosque in Medina by Umayyad Caliph Al-Walid. Later developments of this feature would include additional domes oriented axially to the mihrab dome.[204] Byzantine workmen built the Umayyad Mosque of Damascus and its hemispherical dome for al Walid in 705. The dome rests upon an octagonal base formed by squinches.[109] The dome, called the "Dome of the Eagle" or "Dome of the Gable", was originally made of wood but nothing remains of it. It is supposed to have rested upon large cross beams.[205] Although architecture in the region would decline following the movement of the capital to Iraq under the Abbasids in 750, mosques built after a revival in the late 11th century usually followed the Umayyad model, especially that of the Mosque of Damascus. Domed examples include the mosques at Sarmin (1305-6) and al-Bab (1305). The typical Damascus dome is smooth and supported by a double zone of squinches: four squinches create an eight sided transition that includes eight more squinches, and these create a sixteen-sided drum with windows in alternate sides.[206]

Italian church architecture from the late sixth century to the end of the eighth century was influenced less by the trends of Constantinople than by a variety of Byzantine provincial plans. With the crowning of Charlemagne as a new Roman Emperor, these influences were largely replaced in a revival of earlier Western building traditions. Occasional exceptions include examples of early quincunx churches at Milan and near Cassino.[207] Another is the Palatine Chapel. Its domed octagon design was influenced by Byzantine models such as the Basilica of San Vitale in Ravenna, the Church of Sergius and Bacchus in Constantinople, and perhaps the Chrysotriklinos, or "golden reception hall", of the Great Palace of Constantinople.[208][209] Charlemagne built the Palatine Chapel at his palace at Aachen between 789 and its consecration in 805. The architect is thought to be Odo of Metz, although the quality of the ashlar construction has led to speculation about the work of outside masons.[208] The octagonal domical vault measures 16.5 meters wide and 38 meters high. It was the largest dome north of the Alps at that time.[210] The chapel inspired copies into the 14th century and remained a "focal-point of German kingship". The dome was rebuilt after a fire in 1656 and the interior decoration dates to around 1900.[211]

Venice, Southern Italy and Sicily served as outposts of Middle Byzantine architectural influence in Italy. Venice's close mercantile links to the Byzantine empire resulted in the architecture of that city and its vicinity being a blend of Byzantine and northern Italian influences, although nothing from the ninth and tenth centuries has survived except for the foundations of the first St. Mark's Basilica.[212] This building was presumably similar to Justinian's Church of the Holy Apostles based on its layout, but how it was roofed is unknown.[213] That southern Italy was reconquered and ruled by a Byzantine governor from about 970 to 1071 explains the relatively large number of small and rustic Middle Byzantine-style churches found there, including the Cattolica in Stilo and S. Marco in Rossano. Both are cross-in-square churches with five small domes on drums in a quincunx pattern and date either to the period of Byzantine rule or after.[214] The church architecture of Sicily has fewer examples from the Byzantine period, having been conquered by Muslims in 827, but quincunx churches exist with single domes on tall central drums and either Byzantine pendentives or Islamic squinches.[215] Very little architecture from the Islamic period survives on the island, either.[216]

Much of the Muslim architecture of Al-Andalus was lost as mosques were replaced by churches after the twelfth century, but the use of domes in surviving Mozarabic churches from the tenth century, such as the paneled dome at Santo Tomás de las Ollas and the lobed domes at the Monastery of San Miguel de Escalada, likely reflects their use in contemporary mosque architecture.[217] The Great Mosque of Córdoba, begun in 785 under the last of the Umayyad caliphs, was enlarged by Al-Hakam II between 961 and 976 to include four domes and a remodeled mihrab. The central dome, in front of the mihrab area, transitions from a square bay with decorative squinches to eight overlapping and intersecting arches that surround and support a scalloped dome.[218] These crossed-arch domes are the first known examples of the type and, although their possible origins in Persia or elsewhere in the east remains a matter of debate, their complexity suggests that earlier examples must have existed. The nine bays of the Mosque of Cristo de la Luz, built about 50 years later, contain a virtual catalog of crossed-arch dome variations. After the 10th century, examples can also be found in Armenia and Persia.[219]

The dome of the Great Mosque of Kairouan (also called the Mosque of Uqba), built in the first half of the 9th century, has ribbed domes at each end of its central nave. The dome in front of the mihrab rests on an octagonal drum with slightly concave sides.[220][221] After the ninth century, mosques in North Africa often have a small decorative dome over the mihrab. Additional domes are sometimes used at the corners of the mihrab wall and at the entrance bay. The square tower minarets of two or more stories are capped by small domes. Examples include the Great Mosque of Sfax in Tunisia (founded in the 9th century and later enlarged), the Great Mosque of Algiers (probably of the 11th century), and the Great Mosque of Tlemcen (1303).[222] In Cairo, the martyrium of the Sharif Tabataba (943), an 18 meter square nine-domed open pavilion, is the earliest mausoleum whose plan has survived. The most common type, however, was a small domed cube.[223]

The Fatimids conquered Egypt from North Africa in 969 and established a new architectural style for their new Caliphate.[224] The earliest Fatimid mosque, Al-Azhar, was similar to the earlier Mosque of Ibn Tulun but introduced domed bays at both ends of the qibla wall, in addition to the dome in front of the mihrab, and this feature was later repeated among the mosques of North Africa. Later alterations to the mosque have changed its original form.[225] Egypt, along with north-eastern Iran, was one of two areas notable for early developments in Islamic mausoleums, beginning in the 10th century.[204] Fatimid mausoleums, many of which have survived in Aswan and Cairo, were mostly simple square buildings covered by a dome. Domes were smooth or ribbed and had a characteristic Fatimid "keel" shape profile.[226] The first were built in and around Fustat. Those inside the city were decorated with carved stucco and contrast with the extreme simplicity of those outside the city, such as the four so-called Sab'a Banat (c. 1010) domed squares. Those at Aswan, mostly from the 11th century, are more developed, with ribbed domes, star-shaped openings, and octagonal drums with concave exterior sides which are corbeled outward at the top. They vary in plan as well, with domes sometimes joined with barrel vaults or with other domed mausoleums of different dimensions. The Fatimid mausoleum at Qus is in this Aswan style.[227] Other than the small brick domes used over the bay in front of a mihrab or over tombs, domes were rare. An exception in size was the large dome over the Fatimid palace dynastic tomb.[223] Literary sources describe Fatimid royal domes as part of ceremonial processions and royal recreation.[200] Examples of Fatimid palace architecture, however, described by travelers' accounts as their greatest achievement, have not survived. The ribbed or fluted domes introduced by the Fatimids may derive from a theme in earlier Coptic art, and would be continued in the later architecture of the Mamluks.[228]

The use of corner squinches to support domes was widespread in Islamic architecture by the 10th and 11th centuries.[130] The so-called shrine of Imam al-Dawr in the village of al-Dawr, Iraq, is the earliest known example of a muqarnas dome, although it is unlikely to have been the first of its type. The dome rests on an octagonal base created by four squinches over a square bay. Three levels of muqarnas rise over this and are capped by a small cupola. The muqarnas cells are very large and resemble small squinches themselves. It was finished by 1090 by the court of an Uqaylid vassal of the Abbasid Caliphate of Baghdad and, although there are no surviving examples from Baghdad at this time, the large number of muqarnas domes known to have existed there by the end of the Middle Ages suggests that it could have been the source of the type.[229]

Domes in Romanesque architecture are generally found within crossing towers at the intersection of a church's nave and transept, which conceal the domes externally.[230] Called a tiburio, this tower-like structure often has a blind arcade near the roof.[98] Romanesque domes are typically octagonal in plan and use corner squinches to translate a square bay into a suitable octagonal base.[16] Octagonal cloister vaults appear "in connection with basilicas almost throughout Europe" between 1050 and 1100.[231] The precise form differs from region to region.[230]

The architecture of the areas of northern Italy that were a part of the Holy Roman Empire developed differently from the rest of the Italian peninsula.[232] The earliest use of the octagonal cloister vault within an external housing at the crossing of a cruciform church may be at Acqui Cathedral in Acqui Terme, Italy, which was completed in 1067. This became increasingly popular as a Romanesque feature over the course of the next fifty years. The first Lombard church to have a lantern tower, concealing an octagonal cloister vault, was San Nazaro in Milan, just after 1075. Many other churches followed suit in the next few decades, such as the Basilica of San Michele Maggiore in Pavia and the Basilica of Sant'Ambrogio in Milan.[233]

Interior of St. Mark's Basilica in Venice, Italy

In Venice, the second and current St. Mark's Basilica was built on the site of the first between 1063 and 1072, replacing the earlier church while replicating its Greek cross plan. Five domes vault the interior (one each over the four arms of the cross and one in the center). These domes were built in the Byzantine style, in imitation of the now lost Church of the Holy Apostles in Constantinople. Mounted over pendentives, each dome has a ring of windows at its base.[234] These five windowed domes reflect the addition of windows (within tall drums) in the remodeled Byzantine original. However, the tall outer shells at St. Mark's were not added until after 1204.[213] The higher wooden outer domes with lead roofing and cupolas were added between 1210 and 1270, allowing the church to be seen from a great distance.[234] In addition to allowing for a more imposing exterior, building two distinct shells in a dome improved weather protection. It was a rare practice before the 11th century.[119] The fluted and onion-shaped cupolas of the domes may have been added in the mid-fifteenth century to complement the ogee arches added to the facade in the late Gothic period. Their shape may have been influenced by the open and domed wooden pavilions of Persia or by other eastern models.[186] Initially, only the center dome had one.[213]

Pisa Cathedral, built between 1063 and 1118, includes a high elliptical dome at the crossing of its nave and transept. The marble dome was one of the first in Romanesque architecture and is considered the masterpiece of Romanesque domes. Rising 48 meters above a rectangular bay, the shape of the dome was unique at the time.[235] The rectangular bay's dimensions are 18 meters by 13.5 meters. Squinches were used at the corners to create an elongated octagon in a system similar to that of the contemporary Basilica of San Lorenzo in Milan and corbelling was used to create an oval base for the dome. The tambour on which the dome rests dates to between 1090 and 1100, and it is likely that the dome itself was built at that time. There is evidence that the builders did not originally plan for the dome and decided on the novel shape to accommodate the rectangular crossing bay, which would make an octagonal cloister vault very difficult. Additionally, the dome may have originally been covered by a lantern tower that was removed in the 1300s, exposing the dome, to reduce weight on foundations not designed to support it. This would have been done no later than 1383, when the Gothic loggetta on the exterior of the dome was added, along with the buttressing arches on which it rests.[236]

An aspiring competitor to Pisa, the city of Florence took the opposite side in the conflict between Pope and Emperor, siding with the Pope in Rome. This was reflected architecturally in the "proto-renaissance" style of its buildings.[237] The eight-sided Florence Baptistery, with its large octagonal cloister vault beneath a pyramidal roof, was likely built between 1059 and 1128, with the dome and attic built between 1090 and 1128. The lantern above the dome is dated to 1150.[238] It takes inspiration from the Pantheon in Rome for its oculus and much of its interior decoration, although the pointed dome is structurally similar to Lombard domes, such as that of the later Cremona Baptistery. The domes of Pisa Cathedral and Florence Baptistery may be the two earliest domes in Tuscany and are the two largest until about 1150.[239]

The renovation of Speyer Cathedral, the largest of the Imperial Cathedrals of the Holy Roman Empire and the burial church of the Salian dynasty, was begun around 1080 by the Emperor Henry IV, soon after he had returned from a trip to Canossa in northern Italy. Although the church had only just been consecrated in 1061, Henry called upon craftsmen from across the empire for its renovation. The redesign included two octagonal cloister vaults within crossing towers, one at the east crossing with an external dwarf gallery and one at the west end. This was very soon imitated elsewhere and became the model for later Rhenish octagonal domes, such as those of Worms Cathedral (c. 1120–1181) and Mainz Cathedral (c. 1081–1239).[240] Many German Imperial cathedrals feature domes at their crossings.[80]

Churches in northern Italy after 1100 were designed with vaulting from the outset, rather than as colonnaded basilicas with timber roofs and, like the Rhenish imperial cathedrals, many have octagonal domes with squinches over their crossings or choirs. Examples include Parma Cathedral, rebuilt around 1130, and Piacenza Cathedral (1122-1235).[241] Another example is the domed church of San Fedele in Como (11th to 12th century), similar to the church of St. Maria im Kapitol. The Baptistery of Parma, one of the largest baptisteries, was begun in 1196 and has an octagonal dome.[98] The dome of the Basilica of San Lorenzo in Milan, a tetraconch building with a central space 23.8 meters square, was rebuilt in the Romanesque style after a fire in 1124. Much admired in the Renaissance, its dome collapsed in 1573 and was rebuilt with the present cloister vault.[242]

In southern Italy, the Basilica of San Sabino in Canosa di Puglia was built around 1080 with five domes over its "T-shaped layout", with three domes across the transept and another two out over the nave.[243] The date of construction has been challenged as being decades too late. The multi-domed churches of Cyprus have been proposed as the inspiration for the basilica's domes and for the three-domed naves of later churches in the region, which date mostly from the period of Norman rule, but this is also a topic of debate. San Benedetto at Conversano, the Ognissanti of Valenzano, San Francesco at Trani, and the Cathedral of San Corrado at Molfetta were built in the 11th to 13th centuries with pendentive domes. San Corrado also incorporates "squinch-like niches" between the pendentives and drums of two of its three domes.[244]

In France, the 11th and 12th century Cathedral of Le Puy uses an unusual row of six octagonal domes on squinches over its nave, with the domes at the western end being at least a century later than those at the east end. A seventh dome is located in the normal position for a Romanesque dome on squinches: over the crossing. Other examples of this use over naves are rare and scattered. One is the large church of Saint Hilaire at Poitiers, which seems to have been influenced by Le Puy Cathedral. In 1130, its wide nave was narrowed with additional piers to form suitable square bays, which were vaulted with octagonal domes whose corner sides over trumpet squinches were so narrow that the domes resemble square cloister vaults with beveled corners.[245] The earliest existing large French dome is believed to be the pendentive dome built by 1075 over the crossing of the Collegiate Church of St-Martin at Angers. It reportedly incorporates "pottery" in its structure, a technique used in the late Roman period.[246]

The Crusades, beginning in 1095, also appear to have had an impact on domed architecture in Western Europe, particularly in the areas around the Mediterranean Sea.[247] The Dome of the Rock and the Al-Aqsa Mosque on the Temple Mount of Jerusalem were taken to represent the Temple of Solomon and the Palace of Solomon, respectively. The Knights Templar, headquartered at the site, built a series of centrally planned churches throughout Europe modeled on the Church of the Holy Sepulchre, with the Dome of the Rock also an influence.[248] Examples include the church of the Vera Cruz at Segovia, the church of the Convento do Cristo at Tomar, a rotunda church in Paris destroyed during the French Revolution, and Temple Church in London. The Church of Saint Mary of Eunate was a pilgrims' burial church, rather than a Templar church, but may have been influenced by them.[249] The Mausoleum of Bohemond (c. 1111-18), a Norman leader of the First Crusade, was built next to the Basilica of San Sabino in the southern Italian province of Apulia and has a hemispherical dome in a Byzantine style over a square building with a Greek cross plan.[250]

In southwest France, there are over 250 domed Romanesque churches in the Périgord region alone.[251] A study in 1976 of Romanesque churches in the south of France documented 130 with oval plan domes, such as the those at Saint-Martin-de-Gurson, Dordogne and Balzac, Charente.[252] The oval shape appears to have been a practical solution to rectangular crossing bays.[253] Between the Garonne and Loire rivers there are known to have been at least seventy-seven churches whose naves were covered by a line of domes. Half of them are in the Périgord region. Most date to the twelfth century and sixty of them survive today.[254] The use of pendentives to support domes in the Aquitaine region, rather than the squinches more typical of western medieval architecture, strongly implies a Byzantine influence.[255] The earliest may be Angoulême Cathedral, built from 1105 to 1128. Its long nave is covered by four stone domes on pendentives, springing from pointed arches, the last of which covers the crossing and is surmounted by a stone lantern.[256][257] Cahors Cathedral (c. 1100–1119) covers its nave with two large domes in the same manner and influenced the later building at Souillac.[256] The abbey church at Fontevrault served as a burial place for Plantagenet royalty, including Richard the Lionheart, and is one of the most impressive examples. The earlier domed crossing is preceded by a wider nave covered by four domes, which was begun in 1125. The pendentives are original, but the four nave domes are modern replacements from about 1910.[258] That the domes in this area were arranged in linear series has suggested the contemporary architecture of Cyprus as the inspiration, which was located on a pilgrimage route to the Holy Land.[259] Cyprus had developed its own style of domed basilicas during its period of neutrality between Byzantine and Arab rulers, using three domes of roughly equal size over the nave and very little lighting.[260] The cathedral of S. Front at Périgueux was built c. 1125–1150 and derives its five-domed cruciform plan ultimately from the Church of the Holy Apostles in Constantinople.[256] [261]

The remains of a crossing tower on the French Church of Saint-Jean de Montierneuf from about 1140 suggests an origin for some Spanish domes in a Romanesque and transitional Gothic style.[262] The architectural influences at work here have been much debated, with proposed origins ranging from Jerusalem, Islamic Spain, or the Limousin region in western France to a mixture of sources.[230] During the Reconquista, the Kingdom of León in northern Spain built three churches famous for their domed crossing towers, called "cimborios", as it acquired new territories. The Cathedral of Zamora, the Cathedral of Salamanca, and the collegiate church of Toro were built around the middle of the 12th century. All three buildings have stone umbrella domes with sixteen ribs over windowed drums of either one or two stories, springing from pendentives. All three also have four small round towers engaged externally to the drums of the domes on their diagonal sides.[263] Perhaps the masterpiece of the series, the Salamanca crossing tower has two stories of windows in its drum. Its outer stone fish-scale roof lined with gothic crockets is a separate corbelled layer with only eight lobes, which applies weight to the haunches of the sixteen-sided inner dome.[264]

Another unusual Spanish example from the late 12th or early 13th century is the dome of the Church of the Holy Sepulchre in Torres Del Río, on the Way of St. James. The Way, a major pilgrimage route through northern Spain to the reputed burial place of St. James the Greater, attracted pilgrims from throughout Europe, especially after pilgrimage to Jerusalem was cut off. The difficulty of travel to Jerusalem for pilgrimage prompted some new churches to be built as a form of substitute, evoking the central plan and dome of Jerusalem's Church of the Holy Sepulchre with their own variant. The dome in this case, however, is most evocative of the central mihrab dome of the Great Mosque of Cordoba. Over an octagonal room, the stone dome is formed by sixteen ribs, eight of which intersect with one another in a star pattern to define a smaller octagon at the center of the dome.[265] This is one of a number of Christian crossed-arch dome examples in Spain and the south of France from the end of the 12th century, with patterns based upon the square or octagon. Other examples include the domes of San Miguel de Almazán, Santa Cruz de Olorón, and San Blas Hospital. Contemporary Islamic examples in Spain and North Africa are distinguished from the Christian by the use of thinner and more numerous arches and those at the Alcázar of Seville, the Villena Castle in Alicante, the Great Mosque of Taza, and the minaret of Koutoubia Mosque are examples. The style experienced a revival in early 16th century Spain when one of the crossed-arch domes of the Great Mosque of Córdoba was used as the model for domes at Zaragoza, Teruel and Tarazona.[266]

The Christian domed basilicas built in Sicily after the Norman Conquest also incorporate distinctly Islamic architectural elements. They include hemispherical domes positioned directly in front of apses, similar to the common positioning in mosques of domes directly in front of mihrabs, and the domes use four squinches for support, as do the domes of Islamic North Africa and Egypt. In other cases, domes exhibit Byzantine influences with tall drums, engaged columns, and blind arcades.[267] Examples at Palermo include the Palatine Chapel (1132–1143) and La Martorana (c. 1140s).[268] The church of San Giovanni degli Eremiti has five domes in a T-shaped arrangement and the Church of San Cataldo has three domes on squinches, with both showing clearly Islamic influence.[269]

In Islamic North Africa, there are several early muqarnas domes dating from the twelfth century. The earliest may be an Almoravid restoration between 1135 and 1140 of a series of stucco muqarnas domes over the axial nave of the mosque of the Qarawiyyin in Fez. The existence of a near contemporary example from 1154 in the maristan of Nur al-din in Damascus, Syria, and the earlier example of a muqarnas dome in al-Dawr, Iraq, suggests that the style was imported from Baghdad. Most of the examples of muqarnas domes are found in Iraq and the Jazira, dated from the middle of the twelfth century to the Mongol invasion. The use of stucco to form the muqarnas pattern, suspended by a wooden framework from the exterior vault, was the least common in Iraq, although it would be very popular in North Africa and Spain. Because it used two shells, however, windows were restricted to the bases of the domes. They were otherwise used frequently in this type. In Iraq, the most common form was a single shell of brick, with the reverse of the interior pattern visible on the exterior. The Damascus mausoleum of Nur al-Din (1172) and the shrine of Zumurrud Khatun in Baghdad are examples. A third type is found only in Mosul from the beginning of the thirteenth century. It has a brick pyramidal roof, usually covered in green glazed tiles. Of the five preserved examples, the finest is the shrine of Awn al-Din, which used tiny colored tiles to cover the muqarnas cells themselves and incorporates small muqarnas domes into the tiers of muqarnas supporting the large eight-sided star at the center. This design led to a further developement at the shrine of Shaykh Abd al-Samad in Natanz, Iran.[270]

The architecture of Syria and the Jazira includes the widest variety of forms in the medieval Islamic world, being influenced by the surviving architecture of Late Antiquity, contemporary Christian buildings, and Islamic architecture from the east. There are some muqarnas domes of the Iraqi type, but most domes are slightly pointed hemispheres on either muqarnas pendentives or double zones of squinches and made of masonry, rather than brick and plaster. The domes cover single bay structures or are just a part of larger constructions. Syrian mausoleums consist of a square stone chamber with a single entrance and a mihrab and a brick lobed dome with two rows of squinches. The dome at the Silvan Mosque, 13.5 meters wide and built from 1152-1157, has an unusual design similar to the dome added to the Friday Mosque of Isfahan in 1086-1087: once surrounded by roofless aisles on three sides, it may have been meant to be an independent structure. The congregational mosque at Kızıltepe, with its well integrated dome of about 10 meters, is the masterpiece of Artuqid architecture.[271]

The largest preserved Ayyubid dome is that of the Matbakh al-'Ajami in Aleppo, resting on muqarnas pendentives. It may have been the palace residence of the al-'Ajami family.[272] The mausoleum over the tomb of Iman Al-Shafi‘i (built in 1211) has a large wooden double dome (rebuilt in 1722) about 29 meters high and, with the tombs of al-Malik al-Silah and the so-called Tomb of the Abassid Caliphs, is one of three important Ayyubid tombs in Cairo dating from the first half of the 13th century.[273][274] The domed mausoleum was built 35 years after the madrassa ordered by Saladin at the site in 1176-7, which were introduced in Egypt after 1171 to counter Shia Islam. The only madrassa from the period to partly survive is the 1242 construction by As-Salih Ayyub on the site of the Fatimid Eastern Palace. The 10 meter wide domed tomb at its northern end led to the series of funerary madrassas built in Cairo by the Mamluk Sultans.[223]

The use of domes declined in Western Europe with the rise of Gothic architecture.[80] Gothic domes are uncommon due to the use of rib vaults over naves, and with church crossings usually focused instead by a tall steeple, but there are examples of small octagonal crossing domes in cathedrals as the style developed from the Romanesque.[275] Spaces of circular or octagonal plan were sometimes covered with vaults of a "double chevet" style, similar to the chevet apse vaulting in Gothic cathedrals. The crossing of Saint Nicholas at Blois is an example.[261] The domed "Decagon" nave of St. Gereon's Basilica in Cologne, Germany, a ten-sided space in an oval shape, was built between 1219 and 1227 upon the remaining low walls of a 4th-century Roman martyrium.[276] The ribbed dome rises four stories and 34.55 meters above the floor, covering an oval area 21 meters long and 16.9 meters wide. It is unique among the twelve Romanesque churches of Cologne, and in European architecture in general, and may have been the largest dome built in this period in Western Europe until the completion of the dome of Florence Cathedral.[277][278] The Basilica of St. Anthony of Padua was built between 1231 and 1300, in the early period of Italian Gothic architecture, and features seven domes with a blend of Gothic and Byzantine elements. Similar to St Mark's Basilica in Venice, its nave, transepts, crossing, and the intermediate bay before the choir are covered by domes on pendentives in the Byzantine style. Externally, the crossing dome is covered with a conical spire. The choir dome, which may be later than the others, is uniquely Gothic with ribs.[279] A dome with a pyramidal roof and lantern at the Abbot's kitchen of Glastonbury Abbey dates to the early 14th century.[280] Similar vaulting was built over the kitchen of Newenham Abbey by 1338.[281] Timber star vaults such as those over York Minster's octagonal Chapter house (ca. 1286–1296) and the elongated octagon plan of Wells Cathedral's Lady Chapel (ca. 1320–1340) imitated much heavier stone vaulting.[275] The wooden vaulting over the crossing of Ely Cathedral in England was built after the original crossing tower collapsed in 1322. It was conceived by Alan of Walsingham and designed by master carpenter William Hurley.[282][283] Eight hammer vaults extend from eight piers over the 22 meter wide octagonal crossing and meet at the base of a large octagonal lantern, which is covered by a star vault.[284]

Star-shaped domes are found at the Moorish palace of the Alhambra in Granada, Spain, which contains domed audience halls built to mirror the heavenly constellations. The Hall of the Abencerrajes (c. 1333–91) and the Hall of the two Sisters (c. 1333–54) are extraordinarily developed examples of muqarnas domes, taking the tradition of the squinch in Islamic architecture from a functional element in the zone of transition to a highly ornamental covering for the dome itself. The structural elements of these two domes are actually brick vaulting, but these are completely covered by the intricate mocárabe stalactites. The lacy and star-shaped crossing dome of Burgos Cathedral (1567) may have been inspired by these examples, in addition to that built over the cathedral's octagonal Chapel of the Condestable (1482–94) in the Gothic style.[275]

If an external lantern tower was removed from Pisa Cathedral in the 1300s, exposing the dome, one reason may have been to stay current with more recent projects in the region, such as the domed cathedrals of Siena and Florence. The dome of Siena Cathedral had an exposed profile as early as 1224.[285] Set over an irregular 17.7-metre-wide (58 ft) hexagon with squinches to form an irregular twelve-sided base, the dome of Siena Cathedral has two shells and was completed in 1264.[286] No large dome had ever before been built over a hexagonal crossing. Rapid progress on a radical expansion of the cathedral, which would have involved replacing the existing dome with a larger one, was halted not long after the city was struck with an outbreak of the Black Death in 1348.[287] The dome was originally topped with a copper orb, similar to that over Pisa's dome today, but this was replaced in 1385 by a cupola surmounted by a smaller sphere and cross.[288] The current lantern dates from the 17th century and the current outer dome is a 19th-century replacement.[289]

It was only a few years after the city of Siena had decided to abandon the massive expansion and redesign of their cathedral in 1355 that Florence decided to greatly expand theirs.[290] A plan for the dome of Florence Cathedral was settled by 1357.[291] However, in 1368 the plan was altered at the east end to increase the scale of the octagonal dome, widening it from 62 to 72 braccia, with the intent to further surpass the domes of Pisa and Siena.[292] The construction guilds of Florence had sworn to adhere to the model of the dome created in 1367, with a "quinto acuto" pointed profile, but the scale of this new dome was so ambitious that experts for the Opera del Duomo, the board supervising the construction, expressed the opinion as early as 1394 that the dome could not be accomplished.[293] The enlarged dome would span the entire 42-metre (138 ft) width of the three aisled nave, just 2 meters less than that of the Roman Pantheon, the largest dome in the world.[294] And because the distances between the angles of the octagon were even farther apart at 45.5 metres (149 ft), the average span of the dome would be marginally wider than that of the Pantheon.[295] At 144 braccia, the height of the dome would evoke the holy number of the Heavenly Jerusalem mentioned in the Book of Revelation. By 1413, with the exception of one of the three apses, the east end of the church had been completed up to the windowed octagonal drum but the problem of building the huge dome did not yet have a solution.[294] In 1417, the master builder in charge of the project retired and a competition for dome designs was begun in August 1418.[179] Brunelleschi's dome, designed in 1418, follows the height and curvature mandated in 1367.[292]

In the first half of the fourteenth century, stone blocks replaced bricks as the primary building material in the dome construction of Mamluk Egypt, with the brick domes being only 20 percent of those constructed around 1322. Over the course of 250 years, around 400 domes were built in Cairo to cover the tombs of Mamluk sultans and emirs. Although they kept roughly the same proportions, the shift from brick to stone is also associated with an increase in the average span and height of about 3 to 4 meters, and a decrease in the thickness of the domes. The stone domes are generally 8 to 10 meters in diameter and 7 to 11 meters high. The Mausoleum of Farag Ibn Barquq (1398–1411) is an exceptional case, with a dome 16 meters wide and 12.8 meters tall. The stone domes are generally single shells except at the conical crown, where there is a gap between inner and outer layers filled with earth and rubble and which contains the bases of the metal spires. Double shelled domes are rare, but an example is that of Al-Sultanyya Madrasa from 1360. The domes were constructed in circular rings, with the sizes decreasing towards the top of the dome and, because of this, it is possible that elaborate centering may not have been needed. Collapsed remains of some domes has revealed a layer of brick beneath the external stone, which could have supported and aligned the heavier stone during construction. Although the earliest stone domes do not have them, horizontal connections between the ashlar stone blocks were introduced in the fourteenth century, such as those made of teak wood in a dovetail shape used in the Mausoleum of Farag Ibn Barquq.[296] Dome profiles were varied, with "keel-shaped", bulbous, ogee, and stilted domes, and others being used. On the drum, angles were chamfered, or sometimes stepped, externally and triple windows used in a tri-lobed arrangement on the faces.[297]

Decoration for these first stone domes was initially the same external ribbing as earlier brick domes, and such brick domes would continue to be built throughout the Mamluk period, but more elaborate patterns of carving were introduced through the beginning of the sixteenth century. Early stones domes were plastered externally when not cut precisely enough, but improvements in technique over time would make this unnecessary. Spiral ribs were developed in the 1370s and zigzag patterns were common both by the end of the fourteenth century and again at the end of the fifteenth century. In the fifteenth century, interlaced star and floral designs were used in a tiled pattern.[298] The twin-domes of the Sultaniyya complex (c. 1360) and the narrow dome of Yunus al-Dawadar (c. 1385) are unusual in that they have muqarnas at the base of their external ribs, a feature of ribbed domes in Persia. The first example of the zigzag pattern is on the dome of Mahmud al-Kurdi (1394–95), and at least fourteen subsequent domes also used it. The first example of a dome in Cairo with a star pattern is the mausoleum of al-Ashraf Barsbay. The dome of Qaytbay in Cairo's northern cemetery combines geometric and arabesque patterns and is one of the finest.[299] Internally, the squinches of the zone of transition developed into miniaturized and pointed versions that were used row upon row over the entire expanded zone and bordered above and below by plain surfaces.[300] Bulbous cupolas on minarets were used in Egypt beginning around 1330, spreading to Syria in the following century.[301]

In the fifteenth century, pilgrimages to and flourishing trade relations with the Near East exposed the Low Countries of northwest Europe to the use of bulbous domes in the architecture of the Orient. Although the first expressions of their European use are in the backgrounds of paintings, architectural uses followed. The Dome of the Rock and its bulbous dome being so prominent in Jerusalem, such domes apparently became associated by visitors with the city itself. In Bruges, The Church of the Holy Cross, designed to symbolize the Holy Sepulchre, was finished with a Gothic church tower capped by a bulbous cupola on a hexagonal shaft in 1428. Sometime between 1466 and 1500, a tower added to the Chapel of the Precious Blood was covered by a bulbous cupola very similar to Syrian minarets. Likewise, in Ghent, an octagonal staircase tower for the Church of St. Martin d'Ackerghem, built in the beginning of the sixteenth century, has a bulbous cupola like a minaret. These cupolas were made of wood covered with copper, as were the examples over turrets and towers in the Netherlands at the end of the fifteenth century, many of which have been lost. The earliest example from the Netherlands that has survived is the bulbous cupola built in 1511 over the town hall of Middelburg. Multi-story spires with truncated bulbous cupolas supporting smaller cupolas or crowns became popular in the following decades.[302]

Russian domes[edit]

Saint Basil's Cathedral (1555–61) in Moscow, Russia. Its distinctive onion domes date to the 1680s.

The multidomed church is a typical form of Russian church architecture that distinguishes Russia from other Orthodox nations and Christian denominations. Indeed, the earliest Russian churches, built just after the Christianization of Kievan Rus', were multi-domed, which has led some historians to speculate about how Russian pre-Christian pagan temples might have looked. Examples of these early churches are the 13-domed wooden Saint Sophia Cathedral in Novgorod (989) and the 25-domed stone Desyatinnaya Church in Kiev (989–996). The number of domes typically has a symbolical meaning in Russian architecture, for example 13 domes symbolize Christ with 12 Apostles, while 25 domes means the same with an additional 12 Prophets of the Old Testament. The multiple domes of Russian churches were often comparatively smaller than Byzantine domes.[303][304]

The earliest stone churches in Russia featured Byzantine style domes, however by the Early Modern era the onion dome had become the predominant form in traditional Russian architecture. The onion dome is a dome whose shape resembles an onion, after which they are named. Such domes are often larger in diameter than the drum upon which they are set, and their height usually exceeds their width. The whole bulbous structure tapers smoothly to a point. Though the earliest preserved Russian domes of such type date from the 16th century, illustrations from older chronicles indicate that they were at least used since the late 13th century. Like tented roofs, which were combined with and sometimes replaced domes in Russian architecture since the 16th century, onion domes initially were used only in wooden churches and were introduced into stone architecture much later, where their carcasses continued to be made either of wood or metal on top of masonry drums.[305]

Russian domes are often gilded or brightly painted. A dangerous technique of chemical gilding using mercury had been applied on some occasions until the mid-19th century, most notably in the giant dome of Saint Isaac's Cathedral. The more modern and safe method of gold electroplating was applied for the first time in gilding the domes of the Cathedral of Christ the Saviour in Moscow, the tallest Eastern Orthodox church in the world.[306]

Ottoman domes[edit]

Selimiye Mosque dome in Edirne, Turkey

Ottoman architecture made exclusive use of the semi-spherical dome for vaulting over even very small spaces, influenced by the earlier traditions of both Byzantine Anatolia and Central Asia.[307] The Byzantine dome form was adopted and further developed.[21] The earliest Ottoman mosques were single oblong rooms with either simple tiled pitched roofs of wood or a wooden interior dome. Most of these wooden domes have been lost to fires and replaced by flat ceilings. The earliest masonry domes covered square single room mosques, the archetype of Ottoman architecture.[308] Examples include the Mosque of Orhan Gazi in Gebze and Karagöz Bey Mosque in Mostar.[309] This domed-square unit is the defining element of the three basic Ottoman mosque plans: the single unit mosque, multi-unit mosque, and eyvan (or "iwan") mosque.[310]

The multi-unit mosque uses several domed-squares of similar size along the length of a mosque, or across its width, or both, with the central dome sometimes larger than the others.[310] A style common in the Bursa period, and known as the "Bursa type", is like a duplication of the single-domed square, with one long space divided by an arch into two square bays that are each covered by a dome. A variation of this type has the room covered by one dome and one semi-dome, with additional side chambers. A multi-domed style derived from Seljuk architecture is that of the Ulu Camii, or Great Mosque, which consists of a number of domes of the same size supported by pillars.[311]

The eyvan mosque type (the eyvan being derived from Seljuk architecture) uses domed-square units in a variety of sizes, heights, and details, with only the possible pair of side units being similar sizes.[310]

Early experiments with large domes include the domed square mosques of Çine and Mudurnu under Bayezid I, and the later domed "zawiya-mosques" at Bursa. The Üç Şerefeli Mosque at Edirne developed the idea of the central dome being a larger version of the domed modules used throughout the rest of the structure in order to generate an open space. This idea would become important to the Ottoman style as it developed.[307]

The Beyazidiye Mosque (1501-1506) in Istanbul begins the Classical period in Ottoman architecture, in which the great Imperial Mosques, with variations, resemble the former Byzantine basilica of Hagia Sophia in having a large central dome with semi-domes of the same span to the east and west. The peak of this period, which lasted into the 17th century, came with the architecture of Mimar Sinan. Three of these mosques in Istanbul also add semi-domes to the north and south, doing away with the basilica plan: Şehzade Camii, Sultan Ahmed I Camii, and Yeni Cami.[312] The dome and flanking semi-domes scheme of the central nave of Hagia Sophia are reproduced in three Ottoman mosques: the Beyazidiye Mosque, the Kılıç Ali Pasha Mosque, and the Süleymaniye Mosque.[313] Süleymaniye Mosque, built in Constantinople (modern Istanbul) from 1550 to 1557, has a main dome 53 meters high with a diameter of 26.5 meters. At the time it was built, the dome was the highest in the Ottoman Empire when measured from sea level, but lower from the floor of the building and smaller in diameter than that of the nearby Hagia Sophia.

Another Classical domed mosque type is, like the Byzantine church of Sergius and Bacchus, the domed polygon within a square. Octagons and hexagons were common, such as those of Üç Şerefeli Mosque (1437-1447) and Selimiye Mosque in Edirne.[314] The Selimiye Mosque was the first structure built by the Ottomans that had a larger dome than that of the Hagia Sophia. The dome rises above a square bay. Corner semi-domes convert this into an octagon, which muqarnas transition to a circular base. The dome has an average internal diameter of about 31.5 meters, while that of Hagia Sophia averages 31.3 meters.[315] Designed and built by architect Mimar Sinan between 1568 and 1574, when he finished it he was 86 years old, and he considered the mosque to be his masterpiece.

The first large Imperial Mosque of Istanbul in the imported Baroque style was the Nuruosmaniye Mosque (1748-1755). One of the finest was the Laleli Mosque of 1759-1764.[316]

Italian Renaissance domes[edit]

The Cathedral of Florence with Brunelleschi's dome, Italy

After years of considering options, Filippo Brunelleschi and Lorenzo Ghiberti were made joint leaders of the project to build the dome for Florence Cathedral in 1420. Brunelleschi's plan to use suspended scaffolding for the workers won out over alternatives such as building a provisional stone support column in the center of the crossing or filling the space with earth. The octagonal brick domical vault was built between 1420 and 1436, with Ghiberti resigning in 1433. The lantern surmounting the dome, also designed by Brunelleschi, was not begun until 1446, after his death. It was completed in 1467. He had also planned for a two-story external gallery and cornice to be built at the top of the drum where a strip of unclad masonry can be seen today. Although a portion of it was constructed on the southeast side beginning in 1508, work stopped after the visual effect was criticized by Michelangelo. The dome is 42 meters wide and made of two shells.[317] A stairway winds between them. Eight white stone external ribs mark the edges of the eight sides, next to the red tile roofing, and extend from the base of the dome to the base of the cupola. Each of the eight sides of the dome also conceal a pair of intermediate stone ribs that are connected to the main ribs by means of a series of masonry rings. A temporary wooden tension ring still exists near the bottom of the dome. Three horizontal chains of sandstone blocks notched together and reinforced with lead-coated iron cramps also extend the entire circumference of the dome: one at the base (where radial struts from this chain protrude to the exterior), one a third of the way up the dome, and one two thirds of the way up the dome.[179] Only four major cracks have been observed on the inner dome, compared to about fourteen each on the domes of the Pantheon and St. Peter's Basilica.[318] Although the design of the dome is very different from that of the Pantheon and it is unclear what the influences were, it does share some similarities with earlier and smaller brick domes in Persia. The use of a herringbone pattern in the brick allowed for short horizontal sections of the layers of the dome to be completed as self-supporting units. Over 32 meters in height, it remains the largest masonry dome ever built.[319] The dome is not itself Renaissance in style, although the lantern is closer.[292]

Florence was the first Italian city to develop the new style, followed by Rome and then Venice.[320] Brunelleschi's domes at San Lorenzo and the Pazzi Chapel established them as a key element of the Renaissance architectural style.[80] His plan for the dome of the Pazzi Chapel in Florence's Basilica of Santa Croce (1430–52) illustrates the Renaissance enthusiasm for geometry and for the circle as geometry's supreme form. Twelve ribs between twelve circular windows converge on a small oculus. The circular dome rests on pendentives decorated with circular medallions of Florentine ceramic. This emphasis on geometric essentials would be very influential. The dome of San Sisto in Piacenza (1499–1514) is likewise circular and also includes pendentives with circular medallions.[321] Another early example is Giuliano da Sangallo's 1485 design of a dome on the church of Santa Maria delle Carceri in Prato. Like that of the Pazzi Chapel, the dome is ribbed.[322] Other Renaissance domes with a ribbed or spoked wheel design include that of the Certosa di Pavia (1396–1473) and the Madonna di Campagna in Piacenza (1522–1528).[323]

The combination of dome, drum, pendentives, and barrel vaults developed as the characteristic structural forms of large Renaissance churches following a period of innovation in the later fifteenth century. Under Pope Nicholas V, construction started between 1451 and 1455 on an extension of the old St. Peter's Basilica to create a Latin cross plan with a dome and lantern 100 braccia high over a crossing 44 braccia wide (about 24.5 meters wide). Little more than foundations and part of the choir walls were completed before work stopped with the death of Nicholas V. This innovation culminated in Bramante's 1505–6 projects for a wholly new St. Peter's Basilica, and throughout the sixteenth century the Renaissance set of dome and barrel vault would displace use of Gothic ribbed vaults.[324]

The Tempietto, a small domed building modelled on the Temple of Vesta, was built in 1502 by Bramante in the cloister of San Pietro in Montorio to commemorate the site of St. Peter's martyrdom. It has inspired numerous copies and adaptations since, including Radcliffe Camera, the mausoleum at Castle Howard, and the domes of St. Peter's Basilica, St Paul's Cathedral, the Panthéon, and the U.S. Capitol.[325]

The first church with an oval dome in the Renaissance period was the Sant'Andrea in Via Flaminia, built from 1550 to 1554 by Vignola. Use of the oval dome subsequently spread quickly through Italy, Spain, France, and central Europe.[326] Such domes allowed for a synthesis of the two fundamental church types, the longitudinal and central plan churches, and would become characteristic of Baroque architecture and the Counter-Reformation.[327]

The Villa Capra, also known as "La Rotunda", was built by Andrea Palladio from 1565 to 1569 near Vicenza. Its highly symmetrical square plan centers on a circular room covered by a dome, and it would prove highly influential on the Georgian architects of 18th century England, architects in Russia, and architects in America, Thomas Jefferson among them. Palladio's two domed churches in Venice are San Giorgio Maggiore (1565–1610) and Il Redentore (1577–92), the latter built in thanksgiving for the end of a bad outbreak of plague in the city.[328]

The rebuilding of St. Peter's Basilica had begun in 1506 and continued under a succession of builders over a span of 120 years. Bramante's initial design was for a Greek cross plan with a large central hemispherical dome and four smaller domes around it in a quincunx pattern.[329] Proposed inspirations for Bramante's plan have ranged from some sketches of Leonardo da Vinci to the Byzantine quincunx church and the dome of Milan's Basilica of San Lorenzo.[330] He completed the four massive central piers and the arches linking them by 1512, but cracking in the arches was detected between 1514 and 1534, possibly due to differences in settling resulting from the two eastern piers resting on solid marl and clay, while the other two rested above earlier Roman construction.[331] That the piers and arches were left to stand with incomplete buttressing while construction stopped for over 30 years was also a factor.[332] Among the alterations to the plan made by Giuliano da Sangallo was changing the design of the central dome from being hemispherical to being 9 meters taller, segmental, and ribbed. He strengthened the piers and completed building the pendentives. Michelangelo redesigned the dome to have two shells, a mostly brick internal structure, and three iron chains to resist outward pressure.[333] He further strengthened the piers by eliminating niches in them and the internal spiral staircase.[334] He obtained a decree from Pope Julius III that threatened an interdiction against anyone who altered his design, completed construction of the base for the drum by May 1558, and spent November 1558 to December 1561 creating a detailed wooden model of a hemispherical dome. Construction of the drum was completed a few months after he died in 1564.[335] The dome was later completed by Giacomo della Porta and Domenico Fontana.[329] Della Porta insisted on an elliptical shape for the dome, for structural reasons, and construction began in June 1588. The dome was completed up to the base of the lantern in May 1590, a few months before the death of Pope Sixtus V. The lantern and lead covering for the dome were completed later, with the brass orb and cross being raised in 1592.[336] The ogival dome was built with 16 ribs and an inner diameter of 42.7 meters. It begins above the drum and attico (the decorative strip above the drum), which are about 18 meters tall.[337] The iron chains included in the design to contain the dome's lateral thrust have had to be replace ten times since it was constructed.[338] Giovanni Poleni's 1748 report on the state of the dome, written in response to observed cracking, anticipated the safe theorem by stating "explicitly that the stability of a structure can be established unequivocally if it can be shown that the thrust line lies completely within the masonry."[6] The outside of the drum is decorated with pairs of columns between the large windows. Its external height from the ground to the top of the cross is 136.57 meters (448.1 ft). The dome remains the tallest in the world. The style of the church ushered in what would become known as Baroque architecture, and the dome in particular would have great influence on subsequent designs.

South-Asian and Mughal domes[edit]

The Taj Mahal in Agra, India built by Shah Jahan.

Islamic rule over northern and central India brought with it the use of domes constructed with stone, brick and mortar, and iron dowels and cramps. Centering was made from timber and bamboo. The use of iron cramps to join together adjacent stones was known in pre-Islamic India, and was used at the base of domes for hoop reinforcement. The synthesis of styles created by this introduction of new forms to the Hindu tradition of trabeate construction created a distinctive architecture.[339] Domes in pre-Mughal India have a standard squat circular shape with a lotus design and bulbous finial at the top, derived from Hindu architecture. Because the Hindu architectural tradition did not include arches, flat corbels were used to transition from the corners of the room to the dome, rather than squinches.[21] In contrast to Persian and Ottoman domes, the domes of Indian tombs tend to be more bulbous.[340]

The earliest examples include the half-domes of the late 13th century tomb of Balban and the small dome of the tomb of Khan Shahid, which were made of roughly cut material and would have needed covering surface finishes. The Alai Dawarza, a gate in the Qutb complex built in 1311, has the first dome in India made of finely dressed stone cut into voussoir blocks. Arches transition a square chamber to an octagon, which transitions to a sixteen-sided polygon through the use of corbelled brackets. The cut stone dome over the tomb of Ghiyath al-Din Tughluq (d. 1325) uses alternating rings of shallow and deep stones to produce a better bond with the core material. The use of finely cut stone voussoirs for these domes suggest the migration of masons from the former Seljuk Empire.[341]

Dome from the late 14th century use roughly shaped stones covered in render, due to the dispersal of skilled masons following the movement of the capital from Delhi to Daulatabad and back again. Examples include the Khirki Masjid (c. 1375) and the tomb of Firoz Shah (d. 1388). The domed tomb of Khan-i-Jahan Tilangani (1368) is generally referred to as "the first octagonal tomb in Delhi with the domed central chamber surrounded by an ambulatory verandah with three arched openings on each facet", although it is predated by the tomb of Zafar Khan.[342]

Under the Lodi dynasty there was a large proliferation of tomb building, with octagonal plans reserved for royalty and square plans used for others of high rank, and the first double dome was introduced to India in this period. There are multiple candidates. The tomb of Sikander Lodi was built from 1517 to 1518 and is cited, but is predated by the brick tomb of Zain-ul-Abidin's mother, built around 1465 in Zaina Kadal, Srinagar. The Sabz Burj in Delhi may be earlier still, but is dated to 1530-40 by written sources.[343]

The first major Mughal building is the domed tomb of Humayun, built between 1562 and 1571 by a Persian architect. The central dome likely has a core of brick, as can be seen in the later stripped tomb of Khan-i-Khanan. The central dome is faced with marble blocks in attached to the core by alternating wide and narrow layers and there is evidence of the use of iron cramps to secure them. Iron cramps may also help form a tension ring at the base of the dome. The central double dome covers an octagonal central chamber about 15 meters wide and is accompanied by small domed chattri made of brick and faced with stone. Smaller domes were widely made with rectangular bricks beginning in the 16th century, the necessary curvature being created by tapering the mortar joints.[344] Chatris, the domed kiosks on pillars characteristic of Mughal roofs, was adopted from its Hindu use as a cenotaph.[345]

The Taj Mahal in Agra, also a brick structure clad primarily in marble, was begun in 1632 and mostly completed in 1636; the rest of the extensive complex would not be finished before 1643. The tomb was built for Mumtaz Mahal, a wife of emperor Shah Jahan, after her death in 1631. The central double dome covers a diameter of 22 meters. The inner dome is three meters thick and over 30 meters below the outer dome. The outer dome rests upon drum walls five metes thick.[346] The fusion of Persian and Indian architecture can be seen in the dome's shape: the bulbous shape derives from Persian Timurid domes, and the finial with lotus leaf base is derived from Hindu temples.[21] The inner dome has a decorative triangulated pattern modeled after plaster mold work, but here carved in marble. The entire complex is highly symmetrical. On the western side of the tomb is a red sandstone mosque with three bulbous domes faced with marble, and on the eastern side is mirror-image assembly hall that likewise has three marble domes.[347] At the center of the tomb hall lies the cenotaph of Mumtaz Mahal, with her husband's off-center to the west. The actual sarcophagi lie directly below, in the crypt, but in the same arrangement.[348]

The tomb of Mohammed Adil Shah (d. 1656) in Bijapur is one of the largest masonry domes in the world. Called the Gol Gumbaz, or Round Dome, it has an internal diameter of 41.15 meters and a height of 54.25 meters. The dome was built with layers of brick between thick layers of mortar and rendered on both faces, so that the dome acts as a concrete shell reinforced with bricks. It is 2.6 meters thick at the base.[349] The dome was the most technically advanced to be built in the Deccan, and exemplifies the flowering of art and architecture that occurred during the period of the Adil Shahi Sultanate's greatest extent.[350] Radial cracks were repaired in 1936-7 by the application of reinforcement to the outside of the dome, which was then covered by sprayed concrete.[351] Both the Gol Gumbaz dome and the smaller dome of the Jama Masjid, a 57 foot wide dome also at Bijapur, are above distinctive transition zones consisting of eight intersecting arches that narrow the openings to be covered.[352]

The last major Islamic tomb built in India was the tomb of Safdar Jang (1753–54). It is a brick structure clad in sandstone and marble stripped from the earlier tomb of Khan-i-Khanan (d. 1627). Shallow brick domes cover the perimeter chambers of the building, and the central dome is reportedly triple-shelled, with two relatively flat inner brick domes and an outer bulbous marble dome, although it may actually be that the marble and second brick domes are joined everywhere but under the lotus leaf finial at the top.[353]

The Badshahi Mosque in Pakistan remained the largest mosque ever built until the Grand Mosque in Mecca was constructed in 1986. It has three domes, the largest of which is the central one which reaches 15 m in height and has a diameter of 21.5 m at the central bulging.

Early modern period domes[edit]

The dome of St. Paul's Cathedral in London, England.

In the early sixteenth century, the lanterns of Italian domes spread to Germany as a wood and copper cupola called the welsche Haube ("Italian hood"). This structure gradually adopted the bulbous cupola from the Netherlands, with the first such example being on the tower of the town hall of Emden (1574–76). Other early examples were on the town halls of Brzeg, Silesia (1570–76), Rothenburg ob der Tauber (1572-78), and Lemgo (c. 1589). Early examples in Danzig, such as the tower of the town hall (1561) and the tower of the church of St. Catherine (1634), show Dutch and possibly Russian influence.[354]

Russian architecture strongly influenced the many bulbous domes of the wooden churches of Bohemia and Silesia, such as the 1506 wooden church tower in Pniów and the church of St. Anna in Czarnowancz. This type blended into German rural architecture such that, in Bavaria, bulbous domes less resemble Dutch models than Russian ones. The polygonal domes on the towers of the Frauenkirche in Munich from about 1530 and the hexagonal domes of the town hall of Augsburg from 1615 are examples. Domes like these gained in popularity in central and southern Germany and in Austria in the seventeenth and eighteenth centuries, particularly in the Baroque style. Dresden in particular has outstanding examples, including the lantern over the large central dome of the Frauenkirche (1726–39). German and Austrian influence resulted in many bulbous cupolas in Poland and Eastern Europe from this period, and rural church towers in the Austrian and Bavarian Alps still feature them. However, many bulbous domes were replaced over time in the larger cities in the second half of the eighteenth century in favor of hemispherical or stilted cupolas in the French or Italian styles. In Italy, bulbous domes remained rare, but among them are those of the lantern and side towers of the Basilica of Superga (1717–31).[355]

In Poland, polygonal buildings and earlier medieval towers were often capped with domes in the Renaissance or Baroque styles. The Renaissance domes were generally onion domes stacked on top of one another and separated with so-called lanterns of openwork arcades. An example is the tower at the Basilica of the Holy Trinity in Chełmża. The Baroque domes were characterized by unusual shapes and curves, such as those of Gniezno Cathedral.[356]

Over the course of the seventeenth and eighteenth centuries, developments in mathematics and the study of statics led to a more precise formalization of the ideas of traditional constructive practices with regards to arches and vaults, and there was a diffusion of studies on the most stable form for these structures: the catenary curve. At the same time, developments in Baroque architecture in response to the Protestant Reformation placed greater emphasis on theatricality and the ceremonies at the altar and this expressed itself in new church designs, such as those of Sant'Andrea al Quirinale by Bernini and San Carlo alle Quattro Fontane by Borromini. Both use the oval or elliptical dome to cover plans that synthesize longitudinal and central plan church layouts, allowing clear views of the altar from all points.[327]

After having worked in Rome for seven years, Jacques Lemercier designed the dome at Val-de-Grâce, which was built to commemorate the birth of Louis XIV and includes an inscription around the dome relating to the Bourbon kings.[357] Inspired by St. Peter's Basilica, its dome likewise has two shells, but the outer shell is much taller in order to compensate for the foreshortening effect from viewing the exterior dome from nearby on the ground. The inner shell is stone and the outer shell is wood.[358]

The four years Guarino Guarini, a Theatine monk and mathematician, spent in Paris may have influenced the emphasis on forced perspective and optical effects in his domes, in contrast to the more formalistic architectural design of Rome at that time. He used form, color, and light to give the illusion of greater height in his centralized domed churches. In the Parisian church of Sainte-Anne-la-Roy (1662) and the Church of San Lorenzo (1670–87) in Turin he used interlacing bands or ribs reminiscent of Islamic domes at Iznik or Cordoba, or the Christian example at Torres Del Río. His dome over the Chapel of the Holy Shroud (1667–90) in Turin is supported by six stacked hexagonal layers of six arches each, arranged such that each layer of arches spring from the peaks of the arches in the layer below them. Although the layers form a cone leading to the base of the dome, each is made progressively smaller to exaggerate the appearance of height. The dome itself is a lighter color than the lower levels of the church, also making it appear even farther away.[359] The idea of a large oculus in a solid dome revealing a second dome originated with Guarini.[360] Many decades later, the crossed-arch dome was revived by Bernardo Vittone in projects such as the Chapel of San Luigi Gonzaga.[361][266]

London's Great Fire of 1666, following a devastating outbreak of plague in the city which killed a fifth of its population, spurred the commission of Christopher Wren to rebuild St. Paul's Cathedral, which occurred over the course of 35 years. Robert Hooke, who first articulated that a thin arch was comparable to an inverted hanging chain, advised Wren on how to achieve the crossing dome.[362] The crossing dome, designed in several stages by Christopher Wren as the church was rebuilt between 1677 and 1708, had its initiation with the first plans for modifying Old St. Paul's, even before the fire of 1666. It was "a form of church building," John Evelyn recorded in his diary, "not as yet known in England, but of wonderful grace."[363] When finished, the dome was three layers: an inner dome with an oculus, a decorative outer wood dome covered in lead roofing, and a structural brick cone in between. The brick cone ends in a small dome that supports the cupola and outer roof and the decorated underside of which can be seen through the inner dome's oculus. The structure rises 365 feet (108 m) to the cross at its summit, but is evocative of the much smaller Tempietto by Bramante.[364] The use of the brick cone, in addition to other innovations, allowed the piers beneath the dome to be reduced in size.[358] The iron chains used to encircle the 34 meter wide dome have since been replaced by stainless steel girdles.[365]

Adjacent to a hospital and retirement home for injured war veterans, the royal chapel of Les Invalides in Paris, France, was begun in 1679 and completed in 1708. The dome was one of many inspired by that of St. Peter's Basilica and it is an outstanding example of French Baroque architecture. In 1861 the body of Napoleon Bonaparte was moved from St. Helena to the most prominent location under the dome.

The Sanctuary of Vicoforte in northwest Italy was originally meant to be the official dynastic mausoleum of the House of Savoy, which had governed Piedmont and southwest France since the 15th century, but problems with uneven settlement due to the soil led to a halt in construction and the mausoleum was built elsewhere. After efforts of compensate for the settlement, construction was resumed to complete the building as a basilica. The oval dome, very close to an ellipse, was completed in 1731 and is the largest masonry dome of its kind in the world. It measures 37.15 meters by 24.8 meters at its base and is pierced by eight oval windows and a central oval oculus with a cupola. Although iron rings were used as part of the original construction at three levels to hold the dome together, cracks developed in the dome as the foundation settled further over the centuries. Additional reinforcement was added from 1985–87 to halt their spread.[366] Oval domes are also found in nearby Liguria, such as the church of San Torpete (1730–33) in Genoa, but the use of stone in this region, rather than the brick predominant in the architecture of Piedmont, limited their size. The style of Piedmont spread to Vienna, where Italian architects built oval-plan churches and inspired the building of others, just as Guarini's plan for the church of S. Maria Ettinga in Prague had inspired a group of buildings built in Bohemia between 1698 and 1710.[327]

The oval dome of the Trinity church in Bratislava was built between 1717 to 1745. It is very similar to that of St. Peter's Church in Vienna, which the architect, Antonio Galli Bibiena, had briefly worked on, but is decorated instead by painting in the trompe-l'œil technique for which the Bibiena family is known. The dome of Santa Maria Assumpta (c. 1770) in Sabbioneta, also designed by Bibiena, employs a more complex trompe-l'œil effect. A double dome, the inner dome is an open latticework through which the outer dome can be seen, which is painted to appear to be a clear sky.[367]

Plans for the Church of St. Genevieve, the patron saint of Paris, were approved in 1757 with a dome 275 feet tall over a Greek cross plan. Like St. Paul's Cathedral, the dome consisted of three shells. Unlike St. Paul's, and due to advances in mathematics and engineering, all three shells were built of stone and made a part of a structural system that permitted support by thinner piers and walls.[368]

In the eighteenth century, the study of dome structures changed radically, with domes being considered as a composition of smaller elements, each subject to mathematical and mechanical laws and easier to analyse individually, rather than being considered as whole units unto themselves.[327]

Although never very popular in domestic settings, domes were used in a number of 18th century homes built in the Neo-Classical style, including the 1720s Chiswick House, in West London, and Thomas Jefferson's Monticello, begun in the 1770s.[369] Monticello's dome was the first to be built on an American home.[370]

In the United States, most public buildings in the late 18th century were only distinguishable from private residences because they featured cupolas, such as that of the Maryland State House or the smaller, and more typical, example over the Old State House of Delaware.[371] The wooden dome over the Maryland State House in Annapolis was the first dome on a capitol building in the United States, added between 1785 and 1787. The Massachusetts State House, built in the next decade, included a dome after it was decided that the national capitol building would have one.[372] Several states added prominent domes to their assembly buildings as a result of the choice for the national capitol, and completed them before it was finished.[373] The design for the national capitol building approved by George Washington included a dome modeled on the Pantheon, with a low exterior elevation, but subsequent design revisions resulted in a double dome with a raised external profile on an octagonal drum and construction did not begin until 1822. The interior dome was built of stone and brick except for the upper third, which was made of wood. The exterior dome was wooden and covered with copper sheeting.[374]

Modern period domes[edit]

Geodesic domes of the Eden Project in United Kingdom

New production techniques allowed for cast iron and wrought iron to be produced both in larger quantities and at relatively low prices during the Industrial Revolution. Iron was used in place of wood where fire resistance was a priority. In Russia, which had large supplies of iron, some of the earliest examples of the material's architectural use can be found. Andrey Voronikhin built a large wrought iron dome over Kazan Cathedral in Saint Petersburg.[375] Built between 1806 and 1811, the 17.7 meter wide outer dome of the cathedral was one of the earliest iron domes.[376]

Although iron production in France lagged behind Britain, the government was eager to foster the development of its domestic iron industry. In 1808, the government of Napoleon approved a plan to replace the burnt down wooden dome of the Halle au Blé granary in Paris with a dome of iron and glass, the "earliest example of metal with glass in a dome". The dome was 37 meters in diameter and used 51 cast iron ribs to converge on a wrought iron compression ring 11 meters wide containing a glass and wrought iron skylight. The outer surface of the dome was covered with copper, with additional windows cut near the dome's base to admit more light during an 1838 modification.[377] Cast-iron domes were particularly popular in France.[80]

An early example from Britain is the fanciful iron-framed dome over the central building of the Royal Pavilion in Brighton, begun in 1815 by John Nash, the personal architect of King George IV.[378]

A modern dome of Bashundhara City, the largest shopping mall of South Asia, which is situated in Dhaka Bangladesh.

In 1828, the eastern crossing tower of Mainz Cathedral was rebuilt by Georg Moller with a wrought iron dome.[379] The dome was made of flat iron sections and reinforced with ties that passed through the interior of the dome. Such dome reinforcement was one of the two established techniques, the other being the use of a combination of horizontal rings and vertical ribs.[380] It was later removed in favor of the current structure.[381]

Saint Isaac's Cathedral, in Saint Petersburg, was built by 1842 with one of the largest domes in Europe. A cast iron dome nearly 26 meters wide, it had a technically advanced triple-shell design with iron trusses reminiscent of St. Paul's Cathedral in London.[382] Also reminiscent of St. Paul's dome and that of the Panthéon in Paris, both of which the original designer had visited, the dome of St. Nicholas' Church in Potsdam was added to the building from 1843-49.[383] Included as a possibility in the original late Neoclassical design of 1830 as a wooden construction, iron was used instead by the later architects.[384]

The Neoclassical style popular at this time was challenged in the middle of the nineteenth century by a Gothic Revival in architecture, in what has been termed the "Battle of the Styles". This lasted from about 1840 to the beginning of the twentieth century, with various styles within Classicism, such as Renaissance, Baroque, and Rococo revivals, also vying for popularity. The last three decades of this period included unusual combinations of these styles.[385]

The British Museum Library constructed a new reading room in the courtyard of its museum building between 1854 and 1857. The round room, about 42.6 meters in diameter and inspired by the Pantheon, was surmounted by a dome with a ring of windows at the base and an oculus at the top. Hidden iron framing supported a suspended ceiling made of papier-mâché.[386] A cast iron dome was built between 1860 and 1867 over the reading room of the Bibliothèque nationale in Paris.[80] Inspired by the prestigious British Museum reading room, the first iron dome in Canada was built in the early 1870s over the reading room of the Library of Parliament building in Ottawa. Unlike the British Museum room, the library, which opened in 1876, uses the Gothic style.[387] The dome of the Thomas Jefferson Building of the Library of Congress, also inspired by the reading room dome at the British Museum, was built between 1889 and 1897 in a classical style. It is 100 feet wide and rises 195 feet above the floor on eight piers. The dome has a relatively low external profile to avoid overshadowing the nearby United States Capitol dome.[388]

The current dome over the United States Capitol building, although painted white and crowning a masonry building, is also made of cast iron. The dome was built between 1855 to 1866, replacing a lower wooden dome with copper roofing from 1824.[389] It has a 30 meter diameter.[80] It was completed just two years after the Old St. Louis County Courthouse, which has the first cast iron dome built in the United States.[390] The initial design of the capitol dome was influenced by a number of European church domes, particularly St. Paul's in London, St. Peter's in Rome, the Panthéon in Paris, Les Invalides in Paris, and St. Isaac’s Cathedral in St. Petersburg.[391] The architect, Thomas U. Walter, designed a double dome interior based on that of the Panthéon in Paris.[389]

The Reichstag Palace, built between 1883 and 1893 to house the Parliament of the new German Empire, included a dome made of iron and glass as part of its unusual mixture of Renaissance and Baroque components. Controversially, the 74 meter tall dome stood seven meters taller than the dome of the Imperial Palace in the city, drawing criticism from Kaiser Wilhelm II.[392]

The Hungarian Parliament Building was built in the Gothic style, although most of the 1882 design competition entries used Neo-Renaissance, and it includes a domed central hall. The large, ribbed, egg-shaped dome topped with a spire was influenced by the dome of the Maria vom Siege church in Vienna.[393] It has a sixteen sided outer shell with an iron skeleton that rises 96 meters high, and an inner shell star vault supported on sixteen stone pillars. The Dome Hall is used to display the coronation crown of Hungary and statuary of monarchs and statesmen. The dome was structurally complete by the end of 1895.[394]

Excluding those metal domes that simply imitated multi-shell masonry, metal framed domes such as the elliptical dome of Royal Albert Hall in London (57 to 67 meters in diameter) and the circular dome of Halle au Blé in Paris may represent the chief 19th century development of the simple domed form.[395] Unique glass domes springing straight from ground level were used for hothouses and winter gardens, such as the Palm house at Kew (1844–48) and the Laeken winter garden near Brussels (1875-1876).[396] Elaborate covered shopping arcades, such as the Galleria Vittorio Emanuele II in Milan and the Galleria Umberto I in Naples, included large glazed domes at their cross intersections.[397] The practice of building rotating domes for housing large telescopes was begun in the 19th century, with early examples using papier-mâché to minimize weight.[398] The large domes of the 19th century also included exhibition buildings and functional structures such as gasometers and locomotive sheds.[380] The "first fully triangulated framed dome" was built in Berlin in 1863 by Johann Wilhelm Schwedler in a gasometer for the Imperial Continental Gas Association and, by the start of the 20th century, similarly triangulated frame domes had become fairly common.[399][400] Vladimir Shukhov was also an early pioneer of what would later be called gridshell structures and in 1897 he employed them in domed exhibit pavilions at the All-Russia Industrial and Art Exhibition.[400]

In the late 19th and early 20th centuries, the Guastavino family, a father and son team who worked on the eastern seaboard of the United States, further developed the masonry dome. They perfected a traditional Spanish and Italian technique for light, center-less vaulting using layers of tiles in fast-setting cement set flat against the surface of the curve, rather than perpendicular to it. The father, Rafael Guastavino, innovated with the use of Portland cement as the mortar, rather than the traditional lime and gypsum mortars, which allowed mild steel bar to be used to counteract tension forces.[401] The family built vaults in hundreds of buildings, including the domes of the Basilica of St. Lawrence in Asheville, North Carolina, and St. Francis de Sales Roman Catholic Church in Philadelphia, Pennsylvania.[402] The dome over the crossing of the Cathedral of St. John the Divine in New York City was built by the son in 1909. A part-spherical dome, it measures 30 meters in diameter from the top of its merging pendentives, where steel rods embedded in concrete act as a restraining ring. With an average thickness 1/250th of its span, and steel rods also embedded within the pendentives, the dome "looked forward to modern shell construction in reinforced concrete."[401]

Domes built with steel and concrete were able to achieve very large spans.[80] Reinforced concrete was used to build the Centennial Hall in Breslau, Germany (today Poland) from 1911–13, to commemorate the 100-year anniversary of the uprising against Napoleon. With a 213 foot wide central dome surrounded by stepped rings of vertical windows, it was the largest building of its kind in the world.[403] The 1928 Leipzig Market Hall by Deschinger and Ritter featured two 82 meter wide domes.[80]

The thin domical shell was further developed with the construction of two domes in Jena, Germany in the early 1920s. To build a rigid planetarium dome, Walther Bauersfeld constructed a triangulated frame of light steel bars and mesh with a domed formwork suspended below it. By spraying a thin layer of concrete onto both the formwork and the frame, he created a 16 meter wide dome that was just 30 millimeters thick. The second dome was still thinner at 40 meters wide and 60 millimeters thick.[404] These are generally taken to be the first modern architectural thin shells.[405] These are also considered the first geodesic domes.[406] Beginning with one for the Deutsches Museum in Munich, 15 domed projection planetariums using concrete shells up to 30 meters wide had been built in Europe by 1930, and that year the Adler Planetarium in Chicago became the first planetarium to open in the Western Hemisphere.[407]

Spanish engineer-architect Eduardo Torroja, with Manuel Sanchez, designed the Market Hall in Algeciras, Spain, with a thin shell concrete dome. Built from 1933–34, the shallow dome is 48 meters wide, 9 centimeters thick, and supported at points around its perimeter.[408] Popularized by a 1955 article on the work of Félix Candela in Mexico, architectural shells had their heyday in the 1950s and 1960s, peaking in popularity shortly before the widespread adoption of computers and the finite element method of structural analysis. Notable examples of domes include the Kresge Auditorium at MIT, which has a spherical shell 49 meters wide and 89 millimeters thick, and the Palazzetto dello Sport, with a 59 meter wide dome designed by Pier Luigi Nervi.[409] Early examples used a relatively thick bordering girder to stabilize exposed edges. Alternative stabilization techniques include adding a bend at these edges to stiffen them or increasing the thickness of the shell itself at the edges and near the supports.[410]

Structurally, geodesic domes are also considered shells when the loads are born by the surface polygons, as in the Kaiser Dome, but are considered space grid structures when the loads are born by point-to-point members.[411] Although the first examples were built twenty five years earlier, the term "geodesic domes" was coined by Buckminster Fuller, who invented them independently. He received a patent in 1954. Geodesic domes have been used for radar enclosures, greenhouses, housing, and weather stations.[412] Early examples in the United States include a 53 foot wide dome for the Ford Rotunda in 1953 and a 384 foot diameter dome for the Baton Rouge facility of the Union Tank Car Company in 1958, the largest clear span structure in the world at that time.[413] The U.S. Pavilion at Expo 67 in Montreal, Canada, was enclosed by a 76.5 meter wide and 60 meter tall dome made of steel pipes and acrylic panels. It is used today as a water monitoring center.[414] Other examples include the Amundsen-Scott South Pole Station, which was used from 1975 to 2003, and the Eden Project in the UK, built in 2000.[415]

Tensegrity domes, patented by Buckminster Fuller in 1962, are membrane structures consisting of radial trusses made from steel cables under tension with vertical steel pipes spreading the cables into the truss form. They have been made circular, elliptical, and other shapes to cover stadiums from Korea to Florida.[416] While the first permanent air supported membrane domes were the radar domes designed and built by Walter Bird after World War II, the temporary membrane structure designed by David Geiger to cover the United States pavilion at Expo '70 was a landmark construction. Geiger's solution to a 90% reduction in the budget for the pavilion project was a "low profile cable-restrained, air-supported roof employing a superelliptical perimeter compression ring". Its very low cost led to the development of permanent versions using teflon-coated fiberglass and within 15 years the majority of the domed stadiums around the world used this system, including the Silverdome in Pontiac, Michigan.[417] The restraining cables of such domes are laid diagonally to avoid the sagging perimeter found to occur with a standard grid.[418]

Tension membrane design has depended upon computers, and the increasing availability of powerful computers resulted in many developments being made in the last three decades of the 20th century.[419] Weather-related deflations of some air-supported roofs led David Geiger to develop a modified type, the more rigid "Cabledome", that incorporated Fuller's ideas of tensegrity and aspension rather than being air-supported.[420][418] The pleated effect seen in some of these domes is the result of lower radial cables stretching between those forming trusses in order to keep the membrane in tension. The lightweight membrane system used consists of four layers: waterproof fiberglass on the outside, insulation, a vapor barrier, then an acoustic insulation layer. This is semitransparent enough to fulfill most daytime lighting needs beneath the dome. The first large span examples were two Seoul, South Korea, sports arenas built in 1986 for the Olympics, one 93 meters wide and the other 120 meters wide. The Georgia Dome, built in 1992 on an oval plan, uses instead a triangulated pattern in a system patented as the "Tenstar Dome".[421] The Millennium Dome was completed as the largest cable dome in the world with a diameter of 320 meters and uses a different system of membrane support, with cables extending down from the 12 masts that penetrate the membrane.[422] The first cable dome to use rigid steel frame panels as roofing instead of a translucent membrane was begun for an athletic center in North Carolina in 1994.[423]

The higher expense of rigid large span domes made them relatively rare, although rigidly moving panels is the most popular system for sports stadiums with retractable roofing.[418][424] With a span of 126 meters, Pittsburgh's Civic Arena featured the largest retractable dome in the world when completed for the city's Civic Light Opera in 1961. Six of its eight sections could rotate behind the other two within three minutes, and in 1967 it became the home of the Pittsburgh Penguins hockey team.[425] The first domed baseball stadium, the Astrodome in Houston, Texas, was completed in 1965 with a rigid 641 foot wide steel dome filled with 4,596 skylights. Other early examples of rigid stadium domes include the steel frame Superdome of New Orleans and the cement Kingdome of Seattle.[418] Montreal's Olympic Stadium featured a retractable membrane roof in 1988, although repeated tearing led to its replacement with a non-retractable roof. The Skydome of Toronto opened in 1989 with a rigid system in four parts: one that is fixed, two that slide horizontally, and one that rotates along the edge of the 213 meter wide span. In Japan, the 1993 Fukuoka Dome featured a 222 meter dome in three parts, two of which rotated under the third. Ōita Stadium was built in 2001 as a mostly fixed spherical roof 274 meters wide with two large membrane-covered panels that can slide down from the center to opposite sides.[426]

The variety of modern domes over sports stadiums, exhibition halls, and auditoriums have been enabled by developments in materials such as steel, reinforced concrete and plastics.[427] Their uses over department stores and "futuristic video-hologram entertainment centres" exploit a variety of non-traditional materials.[47]

Symbolism[edit]

Ancient[edit]

The 'Great Stupa' at Sanchi in India, built in the 3rd century BCE.

According to E. Baldwin Smith, from the late Stone Age the dome-shaped tomb was used as a reproduction of the ancestral, god-given shelter made permanent as a venerated home of the dead. The instinctive desire to do this resulted in widespread domical mortuary traditions across the ancient world, from the stupas of India to the tholos tombs of Iberia. By Hellenistic and Roman times, the domical tholos had become the customary cemetery symbol.[428]

In the process of transforming the hut shape from its original pliable materials into more difficult stone construction, the dome had also become associated with celestial and cosmic significance, as evident from decoration such as stars and celestial chariots on the ceilings of domed tombs. This cosmological thinking was not limited to domed ceilings, being part of a symbolic association between any house, tomb, or sanctuary and the universe as a whole, but it popularized the use of the domical shape.[429]

A distinct symbolism of the heavenly or cosmic tent stemming from the royal audience tents of Achaemenid and Indian rulers was adopted by Roman rulers in imitation of Alexander the Great, becoming the imperial baldachin. This probably began with Nero, whose "Golden House" also made the dome an essential feature of palace architecture.[430] The semi-domed apse became a symbol of Imperial authority under Domitian and depictions into the Byzantine period used overhead domes or semidomes to identify the emperor.[47]

The Christian use of domes acknowledged earlier symbolic associations. The traditional mortuary symbolism led the dome to be used in Christian central-type martyria in the Syrian area, the growing popularity of which spread the form. The spread and popularity of the cult of relics also transformed the domed central-type martyria into the domed churches of mainstream Christianity. In Italy in the 4th century, baptisteries began to be built like domed mausolea and martyria, which spread in the 5th century. This reinforced the theological emphasis on baptism as a re-experience of the death and resurrection of Jesus Christ. The dual sepulchral and heavenly symbolism was adopted by early Christians in both the use of domes in architecture and in the ciborium, a domical canopy like the baldachin used as a ritual covering for relics or the church altar. The celestial symbolism of the dome, however, was the preeminent one by the Christian era.[431]

Medieval[edit]

The Green Dome built above the tomb of Muhammad, Abu Bakr and Umar in the Al-Masjid al-Nabawi (Prophet's Mosque) in Medina, Saudi Arabia, dates back to at least the 12th century.

Literary evidence exists that the idea of the cosmic temple had been applied to the Christian basilica by the end of the 4th century, in the form of a speech by Eusebius on a church in Tyre. However, it is only in the mid 6th century that the earliest literary evidence of a cosmological interpretation of a domed church building exists, in the form of a hymn composed for the cathedral church of Edessa. Kathleen E. McVey traces this to a blending by Jacob of Serugh of the two major but contradictory schools of biblical exegesis at the time: the building-as-microcosm tradition of the Antioch school combined with the Alexandrian view of the cosmos and firmament as composed of spheres and hemispheres, which was rejected by the Antioch school.[432] Gold was used as the color of Heaven, and Charles Stewart notes that the emphasis on light from windows beneath the domes of Justinian's imperial commissions corresponds to the Neo-Platonist idea of light as a symbol of wisdom.[433]

Beginning in the late eighth century, portraits of Christ began to replace gold crosses at the centers of church domes, which Charles Stewart suggests may have been an over-correction in favor of images after the periods of Iconoclasm in the eighth and ninth centuries. One of the first was on the nave dome of Hagia Sophia in Thessaloniki, and this eventually developed into the bust image known as the Pantokrator.[434] Otto Demus writes that Middle Byzantine churches were decorated in a systematic manner and can be seen as having three zones of decoration, with the holiest at the top. This uppermost zone contained the dome, drum and apse. The dome was reserved for the Pantokrator (meaning "ruler of all" and usually as a bust in a roundrel), the drum usually contained images of angels or prophets, and the apse semi-dome usually depicted the Virgin Mary, typically holding the Christ child and flanked by angels.[435]

According to Oleg Grabar, the domes of the Islamic world, which rejected such imagery, continued the other traditions. Muslim royalty built palatial pleasure domes in continuation of the Roman and Persian imperial models, although many have not survived, and domed mausoleums from Merv to India developed the form.[436] In the early centuries of Islam, domes were closely associated with royalty. A dome built in front of the mihrab of a mosque, for example, was at least initially meant to emphasize the place of a prince during royal ceremonies. Over time such domes became primarily focal points for decoration or the direction of prayer. The use of domes in mausoleums can likewise reflect royal patronage or be seen as representing the honor and prestige that domes symbolized, rather than having any specific funerary meaning.[437]

Oleg Grabar characterizes forms in Islamic architecture as having relatively low levels of symbolism. While conceding this in a general sense, Yasser Tabbaa maintains that certain forms were initially very highly symbolic and only lost such associations over time. The phenomenon of muqarnas domes, in particular, is an example. Tabbaa explains the development and spread of muqarnas domes throughout the Islamic world beginning in the early 11th century as the visual expression of a theological idea of the universe propounded by the Ash'arites (a modification of the Atomism of Aristotle with Occasionalism), which rose to prominence in Baghdad at this time. Only later was the style used in a purely decorative manner.[438] Doğan Kuban writes that even seemingly minor variations in shape, structure, and functional use had theoretical implications, and were the "result of complex and culturally significant developments in the Islamic world, where the dome and minaret became symbols of Islam."[22] The wide variety of dome forms in medieval Islam reflected dynastic, religious, and social differences as much as practical building considerations.[21]

Modern[edit]

The appearance of the oval in architecture has been extensively discussed by architectural historians. Although not an idea originating in the Renaissance, by the beginning of the 1500s the idea of the oval was "in the air", according to Santiago Huerta.[439] During the Council of Trent, which began the Counter-Reformation of the Catholic Church in response to the Protestant Reformation, the circle and square were declared too pagan for Christian Churches.[440] According to Hanno-Walter Kruft, the effects of the reforms actually adopted by the Council were varied, but the one known written example of the Council's resolutions being applied to architecture, Cardinal Charles Borromeo's Instructiones fabricae et supellectilis ecclesiasticae of 1577, "condemns the circular form as heathenish." The publication was addressed only to Borromeo's own diocese of Milan, but gained currency throughout Europe.[441]

Kendall Wallis writes that the decision to built the national capitol building of the United States with a large dome "took a form laden with symbolic sacred meaning and ascribed a radically secular meaning to it." The decorative use of coffers is meant to evoke a connection with the classical origins of democracy and republicanism. "It represented the legislative power of the republic", sanctified. The ideas of religious association and sky symbolism also persisted in their resonance with the providential overtones of America's sense of its vocation in the world and, more pronounced in the state capitols, in the stars and sky scenes depicted on the domes. Those state capitol domes built after the American Civil War that resembled the second national capitol dome referred symbolically to the Federal government and so to the idea of "the Union".[442]

Both Hitler and Stalin planned, but never completed, enormous domed assembly halls as part of their efforts to establish global capital cities. Hitler's Volkshalle, or "People's Hall", was meant to have a dome 250 meters wide and hold 200,000 people. The Palace of the Soviets in Moscow was meant to be the tallest building in the world with a domed congress hall 100 meters wide at its base for 21,000 world socialist delegates. The foundations were begun for the building on the site of the demolished Cathedral of Christ the Saviour, but technical problems postponed the project and it was abandoned after Stalin's death in the 1950s. R. J. Overy writes that these were meant to be monuments to dictatorship and Utopian civilization that would last for ages.[443]

According to Giovanni Rizzoni, although the dome traditionally represented absolute power, the modern glass dome of the German Reichstag building expresses both the sovereignty of the people, who as tourists are literally above the legislature while touring the dome, and the accessibility of parliamentary democracy, due to the literal transparency of the dome and the window it provides into the legislative chamber below.[444]

Influential domes[edit]

Domes that have been disproportionately influential in later architecture are those of the Pantheon in Rome, Hagia Sophia in Constantinople (modern Istanbul), and the Dome of the Rock in Jerusalem. In Western architecture, the most influential domes built after the early Renaissance exploit of Brunelleschi's Florentine dome have been those of St. Peter's Basilica in Rome and Jules Hardouin-Mansart's dome at Les Invalides in Paris. The dome of St. Peter's Basilica in the Vatican and the dome of St. Paul's Cathedral in London were, among others, the inspirations for the United States Capitol in Washington, which in turn inspired domes of most of the US state capitols.

General types[edit]

A corbel dome

Beehive dome[edit]

Also called a corbelled dome,[445] or false dome,[446] these are different from a 'true dome' in that they consist of purely horizontal layers. As the layers get higher, each is slightly cantilevered, or corbeled, toward the center until meeting at the top. A famous example is the Mycenaean Treasury of Atreus.

Bulbous dome[edit]

Bulbous domes are those which bulge out beyond their base diameters, offering a profile greater than a hemisphere.[5] They became popular in the second half of the 15th century in the Low Countries of Northern Europe, possibly inspired by the finials of minarets in Egypt and Syria, and developed in the 16th and 17th centuries in the Netherlands before spreading to Germany, becoming a popular element of the baroque architecture of Central Europe. German bulbous domes were also influenced by Russian and Eastern European examples.[447] In Islamic architecture, they are found in the Middle East and India, with the Taj Mahal being a famous example. Typically made of masonry, rather than timber, the thick and heavy bulging portion serves to buttress against the tendency of masonry domes to spread at their bases.[5]

A domical vault

Cloister vault[edit]

Main article: Cloister vault

Called domical vaults,[255] polygonal domes,[448] coved domes,[449] gored domes,[450] segmental domes,[47] or pavilion vaults,[451] these are domes that maintain a polygonal shape in their horizontal cross section. The earliest known examples date to the first century BC, such as the Tabularium of Rome from 78 BC. Others include the Baths of Antoninus in Carthage (145-160) and the Palatine Chapel at Aachen (13th - 14th century).[452] The most famous example is the Renaissance octagonal dome of Filippo Brunelleschi over the Florence Cathedral. Thomas Jefferson, the third president of the United States, installed an octagonal dome above the West front of his plantation house, Monticello.[453]

A crossed-arch dome

Crossed-arch dome[edit]

One of the earliest types of ribbed vault, the first known examples are found in the Great Mosque of Córdoba in the 10th century. Rather than meeting in the center of the dome, the ribs characteristically intersect one another off-center, forming an empty polygonal space in the center. Geometry is a key element of the designs, with the octagon being perhaps the most popular shape used. Whether the arches are structural or purely decorative remains a matter of debate. The type may have an eastern origin, although the issue is also unsettled. Examples are found in Spain, North Africa, Armenia, Iran, France, and Italy.[454]

A geodesic dome

Geodesic dome[edit]

Main article: Geodesic dome

Geodesic domes are the upper portion of geodesic spheres. They are composed of a framework of triangles in a polyhedron pattern.[406] The structures are based upon octahedrons or tetrahedrons.[5] Such domes can be created using a limited number of simple elements and joints and efficiently resolve a domes internal forces. Their efficiency is said to increase with size.[455] Although not first invented by Buckminster Fuller, they are associated with him because he designed many geodesic domes and patented them in the United States.[456]

A hemispherical dome

Hemispherical dome[edit]

The hemispherical dome is half of a sphere. According to E. Baldwin Smith, it was a shape likely known to the Assyrians, defined by Greek theoretical mathematicians, and standardized by Roman builders.[457]

An onion dome

Onion dome[edit]

Main article: Onion dome

An onion dome is a greater than hemispherical dome with a pointed top in an ogee profile. They are typically wooden, although masonry examples are found in late Mughal architecture.[5] They are found mostly in eastern architecture, particularly in Russia, Turkey, India, and the Middle East. An onion dome is a type of architectural dome usually associated with Russian Orthodox churches. Such a dome is larger in diameter than the drum it is set upon and its height usually exceeds its width. Similar bulbous domes are also a common feature among Catholic churches in the south of Germany, Austria, and Switzerland.

An oval dome

Oval dome[edit]

An oval dome is a dome of oval shape in plan, profile, or both. The term comes from the Latin ovum, meaning "egg". The earliest oval domes were used by convenience in corbelled stone huts as rounded but geometrically undefined coverings, and the first examples in Asia Minor date to around 4000 B.C. The geometry was eventually defined using combinations of circular arcs, transitioning at points of tangency. If the Romans created oval domes, it was only in exceptional circumstances. The Roman foundations of the oval plan Church of St. Gereon in Cologne point to a possible example. Domes in the Middle Ages also tended to be circular, although the church of Santo Tomás de las Ollas in Spain has an oval dome over its oval plan. Other examples of medieval oval domes can be found covering rectangular bays in churches. Oval plan churches became a type in the Renaissance and popular in the Baroque style.[458] The dome built for the basilica of Vicoforte by Francesco Gallo was one of the largest and most complex ever made.[327]

Parabolic dome[edit]

A parabolic dome is a unique structure in which bending stress due to the uniformly distributed load of its dead load is zero. Hence it was widely used in buildings in ancient times, before the advent of composite structures. However if a point load is applied on the apex of a parabolic dome, the bending stress becomes infinite. Hence it is found in most ancient structures, the apex of the dome is stiffened or the shape modified to avoid the infinite stress.

A sail vault

Sail dome[edit]

Also called sail vaults,[459] handkerchief vaults,[460] domical vaults,[461] pendentive domes,[462] Bohemian vaults,[463] or Byzantine domes, this type can be thought of as pendentives that, rather than merely touching each other to form a circular base for a drum or compound dome, smoothly continue their curvature to form the dome itself. The dome gives the impression of a square sail pinned down at each corner and billowing upward.[9] These can also be thought of as saucer domes upon pendentives.[47]

A large saucer dome

Saucer dome[edit]

Also called a calotte,[9] this is a low pitched, shallow dome that is described geometrically as having a circular base and a segmental section. Many of the largest existing domes are of this shape.

Gaining in popularity from the 18th century onwards, the saucer dome is often a feature of interior design. When viewed from below it resembles the shallow concave shape of a saucer. The dome itself, being often contained in the space between ceiling and attic, may be invisible externally. These domes are usually decorated internally by ornate plaster-work, occasionally they are frescoed.

They are seen occasionally externally in Byzantine churches and Ottoman mosques. Most of the mosques in India, Pakistan, Iran and Afghanistan have these type of domes.

An umbrella dome

Umbrella dome[edit]

Also called gadrooned,[464] fluted,[464] organ-piped,[464] pumpkin,[9] melon,[9] ribbed,[464] parachute,[9] scalloped,[465] or lobed domes,[466] these are a type of dome divided at the base into curved segments, which follow the curve of the elevation.[9] "Fluted" may refer specifically to this pattern as an external feature, such as was common in Mamluk Egypt.[5] The central dome of the Hagia Sophia uses the ribbed method, allowing a ring of windows to be placed between the ribs at the base of the dome. The central dome of St. Peter's Basilica also uses this method.

See also[edit]

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