Germany

Mannheim is a city in the southwestern part of Germany, the third-largest in the German state of Baden-Württemberg with a 2015 population of approximately 305,000 inhabitants. The city is at the centre of the larger densely populated Rhine-Neckar Metropolitan Region which has a population of 2,400,000 and is Germany's eighth-largest metropolitan region.

Leipzig is the most populous city in the federal state of Saxony, Germany. With a population of 582,277 inhabitants (1.1 million residents in the larger urban zone) it is Germany's tenth most populous city. Together with the city of Halle, forms a key metropolitan region. This region represents a major trading intersection and a centre for the service sector, the automobile industry and logistics.

Hamburg, officially the Free and Hanseatic City of Hamburg, is the second-largest city of Germany as well as one of the country's 16 constituent states, with a population of roughly 1.8 million people. The city lies at the core of the Hamburg Metropolitan Region, which spreads across four German federal states and is home to more than 5 million people.

The official name reflects Hamburg's history as a member of the medieval Hanseatic League, a free imperial city of the Holy Roman Empire, a city-state and one of the 16 states of Germany.

Cologne is the largest city in the German federal State of North Rhine-Westphalia and the fourth most populated city (1,060,582 inhabitants by 2015) in Germany (after Berlin, Hamburg, and Munich). It is located within the Rhine-Ruhr metropolitan region which is Germany's largest and one of Europe's major metropolitan areas with a population of 3,573,500.