Geography and urban development of Dresden past 60 years has made Dresden the fourth largest urban area in Germany after Berlin, Hamburg, and Cologne. The most important river in Dresden is the Elbe river, the only navigable body of water to flow through the city. There are also a number of tributaries such as the river Weißeritz. The nearest German cities are Chemnitz (80 km to the southwest), Leipzig (100 km to the northwest) and Berlin (200 km to the north). The Czech capital Prague is about 150 km to the south; the Polish city of Wrocław is about 200 km to the east. There are
Accession of Hamburg to the German Customs Union (Zollverein) to the wishes of all concerned. The Hamburg Senate, like others, had to give up essential parts of its state independence, but this was necessary to achieve an agreement. The Burgerschaft ratified the constitution on 15 May 15, 1867 and it came into force on 1 July 1, 1867, founding the North German Federation. Although Hamburg joined the North German Federation, it remained outside the Customs Union. The federation's constitution included special arrangements for Hamburg and the other Hanseatic cities: Article 34: The Hanseatic cities of Lübeck, Bremen and Hamburg with appropriate districts for this purpose or their surrounding area,