[gary]

Potsdam is 24km south of the city center.

There you can :-

Visit the Großer Refraktor Potsdam -
http://ooo.aip.de/grosser_refraktor/
http://www.potsdam-tourism.com/detai...theme/a-z.html

Walk the Glienicke Bridge -
http://en.wikipedia.org/wiki/Glienicke_Bridge

Visit Schloss Cecilienhof where the Potsdam Conference was held -
http://en.wikipedia.org/wiki/Cecilienhof
http://en.wikipedia.org/wiki/Potsdam_Conference

Visit Sanssouci - the summer palace of Frederick the Great -
http://en.wikipedia.org/wiki/Sanssouci