Fort Louvois

When the high tide rolls up to the shores of Bourcefranc-le-Chapus in southwest France, Fort Louvois is closed in a blockade of waves. It even has its own interior moat that fills around the sea fort.

Built from 1691 to 1694, first under the then-military minister the Marquis of Louvois and then prolific military architect Vauban, the fort was created to protect access to the Passage of Maumusson. However, even though Louis XIV was adamant about its construction, it didn't end up seeing any action until World War II when it was heavily hit.

Now it is a tourist site, with boats arriving while the water is up, and visitors strolling the causeway when the tide is low to the fort that is 1,300 feet from land. Inside, along with a stunning view, there is a museum dedicated to its history as well as oyster farming, a trade that is practiced right alongside the fort and has endured in the area far longer than royal militaristic rule.