There were more than 42,000 incarceration sites, including camps and ghettos, established by the Nazis and their allies between 1933 and 1945. Auschwitz was established in 1940 on the site of a former Austrian military barracks and was itself the coordinating centre of a network of more than forty camps spread across occupied southern Poland. Substantial portions of the central camps have been preserved as a museum by the Polish government since 1947.