Districts of Cologne within city limits), while 174,87 km² (43.2 percent) lie right of the Rhine. In regard to population, Cologne is the largest city in the state of North Rhine-Westphalia and the fourth largest city in Germany. Since the city's foundation in 38 BC, Cologne grew through numerous extensions and incorporation of surrounding municipalities. Since the construction of the Medieval wall in 1180, the area of the old imperial city of Cologne has not changed for more than 600 years and was only extended over the old city walls in 1794, just short before the arrival of French troops and Cologne's incorporation
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,