Mont Saint-Michel at High Tide, Normandy, France — Twice daily, the bay around the mount fills with tidal waters that advance at up to 6 kilometers per hour — famously described as moving 'at the speed of a galloping horse.' At peak spring tides the water rises more than 14 meters, transforming the connected island into a true sea fortress accessible only by boat.
© Corroyer, Édouard Jules, 1837?-1904, Public domain, via Wikimedia Commons
