My thanks to the Fort Louvois Facebook page for these great photos, there are many more on the site.
Fort Louvois is also known as Fort Chapus. It was stated by Francois Ferry in 1691 and completed under Vauban's hand in 1694. It was part of the defences of the La Rochelle / Rochfort area. Renovated in 1875. It saw action in April 1945 when FFI troops liberated the area and the fort came under artillery fire from Germans in Chateau d'Oleron.