Hamburg ; officially the Free and Hanseatic City of Hamburg is the second-largest city in Germany with a population of over 1.8 million.

One of Germany's 16 federal states, it is surrounded by Schleswig-Holstein to the north and Lower Saxony to the south. The city's metropolitan region is home to more than five million people. Hamburg lies on the River Elbe and two of its tributaries, the River Alster and the River Bille.

Rotterdam is the second-largest city and a municipality of the Netherlands. It is located in the province of South Holland, at the mouth of the Nieuwe Maaschannel leading into the Rhine–Meuse–Scheldt delta at the North Sea. Its history goes back to 1270, when a damwas constructed in the Rotte, after which people settled around it for safety. In 1340, Rotterdam was granted city rights by the Count of Holland.

A major logistic and economic centre, Rotterdam is Europe's largest port. It has a population of 633,471 (2017).Rotterdam is known for its Erasmus University, its riverside setting, lively cultural life and maritime heritage. The near-complete destruction of the city centre in the World War II Rotterdam Blitz has resulted in a varied architectural landscape, including sky-scrapers (an uncommon sight in other Dutch cities) designed by renowned architects such as Rem Koolhaas, Piet Blom and Ben van Berkel.

The Rhine, Meuse and Scheldt give waterway access into the heart of Western Europe, including the highly industrialized Ruhr. The extensive distribution system including rail, roads, and waterways have earned Rotterdam the nicknames "Gateway to Europe" and "Gateway to the World".