Mont St Michel

48.6361°N, 1.5116°W.

Mont Saint-Michel in Normandy, northwestern France — a tidal island in the bay between Normandy and Brittany, with a Benedictine abbey constructed in stages from the eighth century CE onward atop the granite rock that forms the island's core. The original abbey was founded in 708 CE by Bishop Aubert of Avranches following a vision of the archangel Michael; the present Romanesque church was built between 1023 and 1085 and the Gothic upper structures (the Merveille — the Marvel) between 1203 and 1228. The island is approximately 1 kilometre off the Normandy coast and is connected to the mainland by a causeway (replaced in 2014 by a bridge to restore the natural tidal flushing of the bay); at high spring tides the island is completely surrounded by water, while at low tide visitors can walk to it across the mudflats. The abbey was used as a prison during the French Revolution and through the mid-nineteenth century. UNESCO World Heritage Site since 1979.

A medieval monastery on a tidal granite island that becomes physically isolated from the European mainland twice a day with the rotation of the moon.