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) Instead of the old international treaties, a constitution bound the states together and solidified the union. Thus the fears of the Hanseatic cities had become groundless. But now it became clear that the other grounds alone were strong enough to keep them away from the Customs Union. Following the Second Schleswig War of 1864, Schleswig and Holstein became a Prusso-Austrian condominium, with Prussia occupying the former and Austria the latter, but on 8 June 1866, Prussian general Von Manteuffel crossed the river Eider into Holstein, which bordered Hamburg on the north. Having warned Austria he was exercising Prussia's condominate right