Valentin submarine pens, Naval bunker complex in Blumenthal, Germany.
The submarine bunker is a massive reinforced concrete structure along the Weser riverbank in Blumenthal that was never completed. Huge concrete blocks and steel frames still stand on the grounds, giving an impression of the intended scale of the manufacturing plant.
Construction began in 1943 and was carried out by thousands of forced laborers under terrible conditions. The structure never progressed beyond its raw state, as Allied bombing raids and the war's end prevented completion.
The name refers to a wartime project for mass production of submarines. Today the site serves as a learning center where visitors can trace the fates of forced laborers through documents and testimonies.
Guided tours run regularly and last around two hours, so visitors should bring weatherproof clothing for any conditions. The grounds are mostly accessible, though some areas remain difficult to reach and are recommended only for mobile visitors.
The roof was designed to withstand direct bomb hits, which explains why concrete layers reach up to seven meters thick in some spots. Despite the enormous construction effort, not a single submarine was ever completed here.
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