Hamburg, officially the Free and Hanseatic City of Hamburg, is the second-largest city in Germany after Berlin and sixth-largest city in the European Union, with a population of over 1.9 million. The Hamburg Metropolitan Region has a population of over 5.1 million and is the tenth-largest metropolitan region by GDP in the European Union. At the base of the Jutland Peninsula, the 110 km (68 mi)-long Elbe estuary begins in Hamburg, at the confluence of the Alster and Bille. Hamburg is one of Germany's three city-states alongside Berlin and Bremen, and is surrounded by Schleswig-Holstein to the north and Lower Saxony to the south. The Port of Hamburg is Germany's largest and Europe's third-largest, after Rotterdam and Antwerp. The local dialect is a variant of Low Saxon.