In 1934, a jeweler rented his shop to the party to be used as a "documentation center," and it was quickly converted into a headquarters and prison for the Gestapo. The residential building was, as fate would have it, left practically untouched by the ravages of war and now houses the largest regional WWII-memorial site in Germany. Now also an exhibit detailing the Nazi atrocities, it is a thorough and eye-opening exploration of Cologne's dark past.