8. The Abandoned Submarine Pens, France
Located in the French port of Brest, these immense concrete structures were built by the Nazis during WWII to house submarines. Today, they sit as imposing ruins, partly submerged and overtaken by vegetation. The dark, vast tunnels are eerily silent, and the heavy atmosphere speaks of wartime horrors. The pens’ cold, industrial feel makes them a perfect setting for a spooky adventure.