The three large blocks that make up the base were built in 1941-43. The largest is Keroman 3 at 170m long and 20m high. This one, open to visitors, housed submarines with graving docks. After the war, the French Navy took possession of the base and set up the second squadron of Atlantic submarines, which was disbanded in 1995. The base was returned to the municipality to become a tourist attraction and today is home to the Grand Large sailing association, as well as nautical industries.