Fort du Roule on high ground above Cherbourg was originally built by Napoleon III in the 1850s to protect the port of Cherbourg. The French Navy used the fort between the wars and excavated tunnels for protected storage.
In World War II, the Germans installed casemates and built more tunnels to protect both ammunition and personnel. The fort was liberated by the US Army on 26 June 1944. Part of the site is still used by the French military but much is open as the Cherbourg Liberation Museum. Some of the tunnels are accessible as part of the visit.