Actually it is not a real beach, there is no sand. Nevertheless it's a nice bar right next to the water and with a perfect view of the Berlin sunset. The building in the background is the German chancellery, the office of Angela Merkel.
Comfortable beach chairs, electronic lounge music and cold drinks are exactly the right things to help stressed business men to unwind in the evening, after a successful business day :-)
It's located on the river bank just opposite to the Hauptbahnhof.
This is how it looked after sunset (about 10pm and still not dark) and it's still very crowded. Am I the only one to get up early in the morning? :-)