Berlin is the capital and largest city of Germany by both area and population. Its 3.7 million inhabitants make it the second most populous city proper of the European Union after London.

The city is one of Germany's 16 federal states, and it is surrounded by the state of Brandenburg, the capital of which, Potsdam, is contiguous with Berlin. The two cities are at the center of the Berlin/Brandenburg Metropolitan Region, which is, with 6 million inhabitants, Germany's third-largest metropolitan region after the Rhine-Ruhrand Rhine-Main regions.