My friend and i visited Berlin for 5 nights and had a great stay in Alex's apartment. The location is great - just a short walk to the closest station, Treptower park and lots of restaurants and shops! Communication with Alex was excellent as he was always reachable. The apartment is very spacious and tidy and the wifi is fast. The only small thing i would note is that it can be a little noisy in the evening from the bar next door, however, this is nothing major and I would definitely love to stay again when next in Berlin!