La Valette Underground Military Museum occupies a complex of tunnels built by German forces during the Occupation of Guernsey (1940–1945). The tunnels were originally designed as fuel storage for U-boats, and the museum preserves both the tunnel structure and an extensive collection of German and British military artifacts from both World Wars.
The collection is one of the best of its kind in the Channel Islands. German uniforms, weapons, vehicles, maps, and equipment from the Occupation sit alongside British military material and personal photographs. The museum is privately run with a passion for detail, and the atmosphere of the original tunnel environment — cool, lit dimly, smelling of old concrete and oil — adds considerably to the impact.
La Valette is a ten-minute walk south of the town centre along the seafront path. It is worth combining with a walk along the coastal cliffs beyond it, which give good views back to the castle and the harbour.