#7 Mont Saint-Michel
Situated off the coast of Normandy in France, is an ancient fortification originally built as a monastery in the 8th century. In the 15th century, King Louis XI used it as a prison. Although accessible to the mainland during low tide, the land on which this towering castle is built becomes an island at high tide. A beautiful landmark, Mont Saint-Michel is part of a UNESCO World Heritage Site, and open to the public. Less than 100 people live on the island, in houses originally built outside the castle walls for farmers and fisher-folk.