Built by Vauban in 1694, Fort Louvois, or "Fort du Chapus" (17C), is located about 500m from the shore, off the aptly named Pointe du Chapus. It can be reached on foot at low tide via a 400m-long submersible causeway that runs between oyster beds and fish nurseries, or by boat at high tide in summer. You can see the keep, the barracks, the food hall and the gunpowder magazine. In summer, shows are put on and games for children are organised.