History of Cologne was considered a substitute for the German University of Strasbourg, which became part of France along with the rest of Alsace. Cologne prospered during the Weimar Republic and progress was made especially in governance, city planning and social affairs. Social housing projects were considered exemplary and were copied by other German cities. As Cologne competed to host the Olympics, a modern sports stadium was erected at Müngersdorf. Beginning of the 1920s civil aviation was permitted once more, and Cologne Butzweilerhof Airport soon became a hub for national and international air traffic, second in Germany only to Berlin Tempelhof Airport. At
NS Documentation Centre of the City of Cologne the best pre-served prisons from the Nazi era, representing an historical asset of national and European importance. Since June, 1997, the permanent exhibition in the EL-DE building has depicted political, social and community life in "Cologne During the Nazi Era." That includes the seizure of power and the power apparatus, propaganda and the "national community," everyday life, youth culture, religion, racism, the genocide of Cologne's Jews and its Sinti and Roma, and opposition, resistance, war and society during war. In addition, temporary exhibitions depict local and national aspects of the Nazi regime. The center also mounts more than 130 events