Postleitzahl
... German for zip code (externer Link)
German zip codes are made up of five numbers. The first digit gives you an idea of where the town is on a map. Lower numbers tend to belong to places more in the south, although the rule cannot be applied to strictly:
03172 A town at the Polish border, very east of Germany (an exception)
10014 Somewhere in Berlin (the capital is an exception to the rule)
25999 Kampen auf Sylt, Insel ganz im Norden
22087 Somewhere in Hamburg (a little bit more south)
30165 Somewhere in Hannover (still a bit further south)
47059 Somewhere in Duisburg by the River Rhine
52070 Aachen, near the main railway station
63477 Dörnigheim by the River Main, middle of Germany
70173 Somewhere in Stuttgart, southwest Germany
87561 Oberstdorf, the southernmost town of Germany
90765 Fürth, much higher up, slightly eastwards
99817 Eisenach, in East Germany (former GDR)