5. Hoover Dam, Nevada/Arizona, USA
At Hoover Dam, tourists are often amazed when pouring a bottle of water over the edge results in the water seemingly flowing upward. This phenomenon is due to powerful updrafts of wind created by the dam’s height and shape, not a reversal of gravity. The dam’s arch-gravity design causes hot air to rise rapidly from its sunlit face, creating a strong updraft that lifts the water. More explanation can be found on the Library of Congress page. (usbr.gov)