It took more than 500 years to build Le Mont-Saint-Michel, one of France’s greatest medieval monuments. Completed in 1521, the abbey lies on an island just off the coast of Normandy. The tower and spire were added in the 19th century.
At low tide, the bay separating the island from the mainland becomes dry, making it possible to reach Le Mont-Saint-Michel on foot. As the tide comes in, however, the rush of water surrounds the abbey with as much as 13.7 meters (44.9 feet) of turbulent sea. The furious tides made the abbey impregnable to attack by medieval armies. Today, armies of tourists visit it each year.