Grunewaldsee

The lake is completely occupied by dogs. If you like barking this place is heaven for you. The noise is unbelievable. On the southern beach you can meet hundreds of Berliners, standing  around watching their dogs play in the water. 

The northwestern beach officially is a place for nudists. But you also meet people who don't like to take off their clothes and of course there are lots of... yes, dogs.

If you are biking, watch out for them, because they all are off the leash and like to jump around bicycles.