Seen from the polders before taking the access footbridge, Mont-Saint-Michel looks like a gigantic UFO sitting on the grass. When one approaches it, depending on the tide, it either lies on a vast expanse of sand and water, or it seems to float on the sea illuminated by the rays of the sun. The huge abbey was built on a 80m-long platform created from scratch by medieval builders. Supported by vaulted crypts, this immense structure is a Romanesque and Gothic technological feat.