Around the 7. Century a Slavic tribe came from Eastern Euope and settled on this spot. At that time the area was an island.
It was expanded during the years until 1157 when Margrave Albert the Bear came to power and a new Spandau was made at todays Zitadel of Spandau.
1237 the first Berlin was mentioned, it was located on todays Museumsinsel (Island of Museums.
http://www.stadtentwicklung.berlin.de/download/denkmaltag2008/spandauer-burgwall.jpg
http://en.wikipedia.org/wiki/History_of_Berlin