Birgit's Sunny Room Dachterrasse is a great place to stay.
First: the building is in the heart of Kreuzberg, 2 minutes away from Kottbusser Tor, a fantastic location.
Second: The room is BIG, lot of space for bags, clothes and a comfy real double bed.
Third: it is REALLY "Sunny", being at the last floor, it has windows, ceiling windows and a wonderful terrace with great views of Berlin.
Last but not least: Birgit is very nice, we could have breakfast, use the kitchen and the fridge.

One warning: the flat is at the 5th floor with no elevator. We had no problem, but it could be annoying if you hate stairs, lol.