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
Postage stamps and postal history of Hamburg which belonged to Denmark at that time, was delivered by a Hamburg postal agent, as there was a Hamburg postal agency on Heligoland. On 1 January 1852, Hamburg joined the German-Austrian Postal Union. Since 1866, Hamburg was part of the North German Confederation, which took over the postal service in the North German Postal District on 1 January 1868. The first postage stamps of the Hamburg City Post Office were introduced on 1 January 1859. They were rectangular and in the middle was the coat of arms of the city, overlaid with the value number. Below that is the word