Cologne is the largest city of Germany's most populous federal state of North Rhine-Westphalia and the fourth-most populous city in Germany. With slightly over a million inhabitants within its city boundaries, Cologne is the largest city on the Rhine and also the most populous city both of the Rhine-Ruhr Metropolitan Region, which is Germany's largest and one of Europe's major metropolitan areas, and of the Rhineland. Centered on the left bank of the Rhine, Cologne is about 45 kilometres southeast of North Rhine-Westphalia's capital of Düsseldorf and 25 kilometres northwest of Bonn. It is the largest city in the Central Franconian and Ripuarian dialect areas.
The city's Cologne Cathedral is the seat of the Catholic Archbishop of Cologne. There are many institutions of higher education in the city, most notably the University of Cologne, one of Europe's oldest and largest universities, the Technical University of Cologne, Germany's largest university of applied sciences, and the German Sport University Cologne, Germany's only sport university. Cologne Bonn Airport is Germany's seventh-largest airport and lies in the southeast of the city.