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
Historical Archive of the City of Cologne libraries that did not suffer major losses during the French occupation in the early years of the 19th century. After the secularization of abbeys and colleges of canons in Cologne in the early years of the 19th century, the French government ordered their archives to be stored in the state archives in Düsseldorf. It was not until 1949 that a mayor of Cologne succeeded in recovering 19,000 charters and many other records for the Cologne municipal archives. In 1818, the city of Cologne was bequeathed Ferdinand Franz Wallraf's major collection of art, books and manuscripts. After Wallraf's death in 1824,