Also known as fort Chapus, built by François Michel Le Tellier de Louvois, Louis XIV's minister, foundations were put up from 1691, 400 meters from the shore. Just imagine the workers' job, forced to relieve day and night in order to take advantage of the low tide! Louvois died in 1691 and he never saw his plan completed. So the fort would be oval, horseshoe-shaped, linked to the land by a submersible roadway only opened two hours before and after the low tide!
With its central keep and its strong fortifications, the fort is in front of Oléron's castle, ideal to cover the horizon and prevent from Spanish forays. Indeed, citadels and surrounding walls appeared on the coasts of Charente during 17th and 18th centuries...