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
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