Le Mont-Saint-Michel is a tidal island and mainland commune in Normandy, France.
The island lies approximately one kilometre off the country's north-western coast, at the mouth of the Couesnon River near Avranches and is 7 hectares in area. The mainland part of the commune is 393 hectares in area so that the total surface of the commune is 400 hectares.As of 2017, the island had a population of 30.The commune's position—on an island just a few hundred metres from land—made it accessible at low tide to the many pilgrims to its abbey, but defensible as an incoming tide stranded, drove off, or drowned would-be assailants. The island remained unconquered during the Hundred Years' War; a small garrison fended off a full attack by the English in 1433. Louis XI recognised the reverse benefits of its natural defence and turned it into a prison. The abbey was used regularly as a prison during the Ancien Régime.
Wikipedia https://en.wikipedia.org/wiki/Mont-Saint-Michel
Coordinates 48°38'7.883" N -1°30'36.926" E