Bunker Valentin was constructed near Bremen between 1943 and 1945 as an enormous assembly facility for Germany’s Type XXI submarines. Up to 10,000 forced laborers, prisoners of war, concentration camp prisoners and other captives worked on its construction under brutal conditions, and thousands died. Allied bombing halted the project shortly before the end of the war. The massive concrete structure survives today as both an extraordinary piece of wartime engineering and a memorial to those forced to build it.

I photographed Bunker Valentin in Germany in 1999. The overwhelming scale of the structure is what first confronts you, but its size becomes disturbing once you understand who built it and under what conditions. It is one of the places where the physical power of a ruin and the human history behind it are impossible to separate.