Hitler took a personal interest in architecture and worked closely with state architects Paul Troost and Albert Speer to create public buildings in a neoclassical style based on Roman architecture. Speer constructed imposing structures such as the Nazi party rally grounds in Nuremberg and a new Reich Chancellery building in Berlin. Hitler's plans for rebuilding Berlin included a gigantic dome based on the Pantheon in Rome and a triumphal arch more than double the height of the Arc de Triomphe in Paris. Neither structure was built.
Nazi Germany maintained concentration camps (German: Konzentrationslager, KZ or KL) throughout the territories it controlled before and during the Second World War. The first Nazi camps were erected in Germany in March 1933 immediately after Hitler became Chancellor and his Nazi Party was given control of the police by Reich Interior Minister Wilhelm Frick and Prussian Acting Interior Minister Hermann Göring. Used to hold and torture political opponents and union organizers, the camps initially held around 45,000 prisoners. In 1933–1939, before the onset of war, most prisoners consisted of German Communists, Socialists, Social Democrats, Roma, Jehovah's Witnesses, homosexuals, and persons accused of 'asocial' or socially 'deviant' behavior by the Germans.