St Michael’s Mount (Cornish: Karrek Loos yn Koos, meaning “hoar rock in woodland” is a tidal island in Mount’s Bay, Cornwall, United Kingdom. The island is a civil parish and is linked to the town of Marazion by a man-made causeway of granite setts, passable between mid-tide and low water. It is managed by the National Trust, and the castle and chapel have been the home of the St Aubyn family since approximately 1650.

Historically, St Michael’s Mount was a Cornish counterpart of Mont-Saint-Michel in Normandy, France (with which it shares the same tidal island characteristics and the same conical shape, though it is much smaller, at 57 acres [23 ha], than Mont St Michel which covers 247 acres [100 ha]), when it was given to the Benedictine religious order of Mont Saint-Michel by Edward the Confessor in the 11th century.

https://en.wikipedia.org/wiki/St_Michael%27s_Mount