It is connected to the mainland via a thin natural land bridge, which before modernization was covered at high tide, and revealed at low tide. Thus, Mont Saint Michel gained a mystical quality, being an island half the time, and being attached to land the other. In 1879, the land bridge was fortified into a true causeway.
The tides in the area shift quickly, and has been described by Victor Hugo as "á la vitesse d'un cheval au galop" or as swiftly as a galloping horse. The tides can vary greatly, at roughly 14 meters between high and low water marks.
It is a World Heritage Site.