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
Transport in Cologne German limited access highway ("autobahn") was opened in 1932 between Cologne and Bonn. Today, this is A 555. In 1965 Cologne became the first German city to be fully encircled by a beltway. Shortly after the Second World War reconstruction plans by, among others, Rudolf Schwarz called for a downtown bypass freeway (the ) as a centerpiece of rebuilding the city. These schemes were only partially executed though, due to opposition by environmental groups. The completed section became "Bundesstraße (Federal Road) B 55a" which begins at the "Zoobrücke (Zoo Bridge)" and meets with A 4 and A 3 autobahns at