The Fort can be visited
Fort Énet

Fort Énet, a fortification, is located in the Pertuis d'Antioche in Charente-Maritime, France. It was built to protect the Rochefort arsenal from British Royal Navy attacks and forms a defensive line with other fortresses in the region.
History+
Construction of Fort Énet began in 1810 under the reign of Napoleon I. This decision followed the naval battle in the Basque Roads in 1809, which highlighted the need for strengthened coastal defenses. The fortress was part of a larger defense system that also included Fort Boyard and Fort de la Rade on Île-d'Aix.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://commons.wikimedia.org/wiki/File:Fort_%C3%89net_001.jpg
This description draws on the facts documented in the linked Wikipedia article; Wikipedia content is licensed under CC BY-SA 4.0. Wording and editing: Mobile History.
Location: 46.0036, -1.1432