Cologne is Germany's fourth-largest city (after Berlin, Hamburg, and Munich), and is the largest city both in the German Federal State of North Rhine-Westphalia and within the Rhine-Ruhr Metropolitan Area, one of the major European metropolitan areas with more than ten million inhabitants.

Cologne is located on both sides of the Rhine River. The city's famous Cologne Cathedral (Kölner Dom) is the seat of the Catholic Archbishop of Cologne. The University of Cologne (Universität zu Köln) is one of Europe's oldest and largest universities.

Cologne was founded and established in the first century AD, as the Roman Colonia Claudia Ara Agrippinensium in Ubii territory. It was the capital of the Roman province of Germania Inferior and the headquarters of the military in the region until occupied by the Franks in 462. During the Middle Ages it flourished as one of the most important major trade routes between east and west in Europe.

Cologne was one of the leading members of the Hanseatic League and one of the largest cities north of the Alps in medieval and renaissance times. Up until World War II the city had undergone several other occupations by the French and also the British. Cologne was one of the most heavily bombed cities in Germany during World War II. The bombing reduced the population by 95% and destroyed almost the entire city. With the intention of restoring as many historic buildings as possible, the rebuilding has resulted in a very mixed and unique cityscape.

Cologne is a major cultural center of the Rhineland; it is home to more than thirty museums and hundreds of galleries. Exhibitions range from local ancient Roman archeological sites to contemporary graphics and sculpture. The Cologne Trade Fair hosts a number of trade shows such as Art Cologne, imm Cologne, Gamescom, and the Photokina.

The metropolitan area encompasses over 405 square kilometres (156 square miles), extending around a centerpoint that lies at 50° 56' 33 latitude and 6° 57' 32 longitude. The city's highest point is 118 m (387.1 ft) above sea level (the Monte Troodelöh) and its lowest point is 37.5 m (123.0 ft) above sea level (the Worringer Bruch). The city of Cologne lies within the larger area of the Cologne Lowland, a cone-shaped area of southeastern Westphalia that lies between Bonn, Aachen and Düsseldorf.