The U-boat Bunker Keroman 3 (K3) is a massive reinforced concrete structure located in the port city of Lorient, France. Constructed by Nazi Germany during the Second World War, it was a key component of the Keroman submarine base, designed to provide secure servicing, repair, and supply facilities for U-boats operating in the Atlantic. Its formidable construction, with walls and roofs several meters thick, was intended to withstand Allied air raids and bombardment.
After the liberation of France, the strategic installation was repurposed by the French Navy. It remained in active military use for decades, serving various naval functions until the 1990s. This post-war continuity of use helped preserve the structure's integrity, distinguishing it from many other abandoned Atlantic Wall fortifications.
Today, Keroman 3 stands as a designated historical monument and a major tourist attraction. It is open to the public, offering a stark, tangible reminder of Lorient's pivotal role in the Battle of the Atlantic and the broader history of the U-boat war. The bunker's preservation allows visitors to directly experience the scale and ambition of German naval engineering projects on the French Atlantic coast.