Mont Saint-Michel is a granite island a kilometre off the coast of Normandy, in northern France, crowned by an abbey that has stood there since 708 and ringed by a village and ramparts, in a bay whose tides drain fifteen kilometres out over the sand and come back daily at the pace of a walking horse. The abbey was born of a dream: three times the archangel Michael told Bishop Aubert of Avranches to build on the rock, and legend says he made his point the third time by burning a hole in the bishop's skull with his finger; the Benedictines followed, and over the Middle Ages the church and the Gothic buildings of the Merveille were raised on the summit in tiers, a pilgrimage and a fortress that the English never took in the Hundred Years' War. For seventy years after the Revolution it was a prison, the Bastille of the Seas, before the monks came back. The visit climbs the Grande Rue from the island's one gate, a steep cobbled street wedged between medieval houses, inns and shops, to the abbey, whose west terrace and the ramparts facing the open bay give the clearest line on the sea.
The bay funnels the Atlantic into a shrinking, almost flat basin, which is why its tides are the highest in continental Europe, up to fourteen metres, and the tides are rated on a scale of 20 to 120; only when the coefficient passes about 110 does the sea cover the last ramp of the bridge and turn the mount back into an island, most reliably around the equinoxes, watched from the ramparts as the water sweeps in. At low tide the bay is crossed barefoot on the wet sand with a licensed guide, the only safe way, since quicksand and the returning sea take walkers. After dark the floodlights wash the abbey and the gilded archangel on the spire catches the light. Mont Saint-Michel is a church on a rock in the sea, and the sea still decides when it is an island.