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The operators of the small optical illusion site (which is about 150 feet in diameter) claim at that location the laws of physics and gravity do not apply and provide a number of illusions in support of these claims, where water seems to flow upwards, people seem to be standing in slanted positions etc.
The Mystery Spot is a gravity hill, a tilt-induced visual illusion. The illusion experienced by visitors results from the oddly tilted environment as well as standing on a tilted floor. Inside the tilted room of the Mystery Spot, misperceptions of the height and orientation of objects occur.
Even when people are standing outside on a level ground, the slant of the building in the background causes misperceptions as we judge the height of people using the slant of the roof rather than the true horizon.