Mont Saint-Michel has been the subject of traditional, but nowadays good-humoured, rivalry between Normans and Bretons. Bretons claim that since the Couesnon River marks the traditional boundary between Normandy and Brittany, it is only because the river has altered its course over the centuries that the mount is on the Norman side of the border. This legend amuses the area's inhabitants, who state that the border is not located on the Couesnon River itself but on the mainland, 4 km to the west.