In 1919 the regulations of the Treaty of Versailles finished the production and the area was transformed into an airfield. There had been regular Zeppelin flights to Friedrichshafen and even to London from 1919 on, though in the following years most of the aviation moved to Tempelhof Airport. The former zeppelin manufacturing halls were turned into the Staaken Studios and used as the location for various film productions, e.g. parts of Fritz Lang's "Metropolis". In 1929 the estate was sold to the City of Berlin, while parts of the airport were still used by the Deutsche Luft Hansa for flight training and maintenance purposes. In "Albrechtshof" the Demag ("Deutsche Maschinenfabrik AG") built Panther tanks during World War II using forced labour of over 2,500 prisoners held in the nearby Falkenhagen labour camp, a subcamp of the Sachsenhausen concentration camp.