Fort Louvois

What it is

Fort Louvois, also called Fort du Chapus, is a horseshoe-shaped fort built on a rock in the middle of the strait that separates the mainland from the island of Oléron, opposite the port of Bourcefranc-le-Chapus. It was begun in 1691 to plans by the Minister of War, the Marquis de Louvois, under the direction of the engineer François Ferry; on Louvois's death, Vauban scaled the project down and the work ended in 1694. It guarded the southern passage to the Rochefort arsenal, via the Pertuis de Maumusson. It is called the little brother of Fort Boyard.

What makes it special is the approach. At low tide you walk along a cobbled causeway of about 400 m across the seabed; at high tide the fort is surrounded by water and is reached by boat.

What you see

Inside you walk through the courtyard, the barracks, the provisions store, the powder magazine and the guardroom. The keep, separated from the rest by a moat that fills with the tide, is a five-level crenellated tower of about 24 m with a corner turret, and the fort's best viewpoint over the strait and the island. Since 1972 it has housed a small oyster museum and an exhibition on the fort's history, with models of the Charente coast fortifications.

The fort was bombed in September 1944, during the liberation of Marennes, and was flooded in the 2010 storm Xynthia, in which it lost its drawbridge. It belongs to the commune of Bourcefranc-le-Chapus and has been a historic monument since 1929. The visit takes about an hour.

Hours and tides

In 2026 it opened from 4 April to 1 November. The hours change each day with the tide and are published month by month, as a PDF, on the fort's website. The ticket office closes 45 minutes earlier. Check the calendar for the day you go and the Fort Louvois tides and hours page before setting off. Out of season it is closed.

Prices

• Adult: €9.50.
• Under-14s: €4.50; under-4s, free.
• Family (two adults and two children): €24.
• Reduced: €7.50 with a disability and €6 for students, with proof.

The high-tide boat is free. Individual tickets cannot be booked: they are bought there.

Getting there

It all starts at the Le Chapus oyster port, in Bourcefranc-le-Chapus, just before the Oléron bridge. On foot it is about five minutes along the causeway if the tide allows; by boat, about ten. Wear shoes with grip: the causeway is wet and slippery.

If you are sleeping nearby, Le Terminus is in Bourcefranc-le-Chapus itself.

With children, dogs and accessibility

Children like arriving on foot across the sea; at the keep, hold little ones by the hand. There are no toilets in the fort: use the public ones at the port beforehand. You cannot picnic inside either. Dogs are not allowed. The causeway and the interior, with stairs and uneven floors, are not comfortable with a wheelchair or pushchair; ask at the fort before going.

To eat oysters afterwards, the cabins on the La Cayenne canal, such as La Cabane aux Marées, are a few minutes away by car, in Marennes. Across the bridge, Le Château-d'Oléron completes the morning.