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 the 1897 building has been used as a private library by Gerling, a large insurance company. In 1971, a six-story archive building by architect Fritz Haferkamp was built on Severinstraße in the southern part of Cologne's city center. An underlying principle of the design was to protect archival records from fluctuations in weather and climate while creating a balanced room climate. In a move away from the contemporary popularity of electromechanical air conditioning, Haferkamp preferred a structural-physical, self-regulating solution that needed only little additional climate technology. As the "Cologne Model", the building became a model for many later archive buildings