Date visited 28 September 2017
The French submarine Espadon is preserved as a museum ship at St Nazaire, inside the concrete bunker that was built over the entry lock for the basin at St Nazaire. The bunker is only a stone's throw away from the dock gates that were crashed by Campbeltown during the St Nazaire Raid, and one of the guns from Campbeltown is mounted on the roof of the bunker as a memorial. Across the basin are the bomb-proof St Nazaire submarine pens. Photographs cannot really capture how massive that structure is - or how solid it is. Even though the rest of the town was largely flattened by bombing during the war, the bunker survived relatively unscathed and was still in German hands on VE-day. I wouldn't be surprised if it outlasted humanity.
Links and References:
George, A, 2018, Espadon: The first French submarine under the Arctic ice, Warship World, 15 (12), pp40-42.