The Tide of Every 18 Years or So

How the Mont Saint-Michel Abbey gets its stunning perennial moat.

Last month, visitors and residents of the Mont Saint-Michel Abbey, roughly 225 miles west of Paris, found themselves quickly cut off from the mainland, surrounded by the rising waters. The Associated Press reported that land for sheep surrounding the 11th-century site suddenly became seabed as high tide water rushed in. The video above explains the factors that conspired to cause the phenomenon.