The Free and Hanseatic City ofHamburg ( Freie und Hansestadt Hamburg ) is Germany's second-largest city and, at the same time, one of Germany's 16 federal states or Bundesländer. Prior to the formation of the modern German state, Hamburg for centuries enjoyed a status as de facto independent city state and regional power and trade hub in the North Sea. Although situated over 100 km (62 mi) upriver from the North Sea on the Elbe, Hamburg has been one of Europe's most important ports for centuries, as reflected in its full name referencing the Hanseatic League. The city was built upon a number of islands formed by the wide river and its larger and smaller tributaries, and a huge part of its southern half is occupied by the massive port.