The Fort can be visited
Fort de la Fraternité

The Fort de la Fraternité is a historic fortification located on the Îlot du Diable in Roscanvel, France. It was originally designed as part of the defenses for the Goulet de Brest.
History+
The origins of the Fort de la Fraternité date back to 1695, when a gun battery was established here. In 1791, it was expanded into a full-fledged fort. Throughout the 19th century, the complex underwent various modifications. However, by 1870, the fort was abandoned by the military and subsequently used as a storehouse for wood and lime. A lime kiln from 1800 and the limestone seam on the site, exploited until 1875, underscore this civilian reuse. During World War II, in 1942, the Germans added a casemate to the facility.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://commons.wikimedia.org/wiki/File:Fort_fraternite_1.jpg?uselang=fr
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: 48.3076, -4.5730