Wannsee

Altough this is one of Berlin's greater lakes it's hard to find a place to swim. The lake is ok if you like to sail but for having a bath you are restricted to the public open air swimming pool on the eastern beach. The lake is quite famous in Germany and of course you can't get in for free.

A good thing about Wannsee is ferry #10 which takes you from Wannse to the district of Kladow. It's a nice 30 minute trip and if you already have a valid U-Bahn or S-Bahn ticket you don't have to pay for it.