Rita was very welcoming and helpful, maybe the best landlady in Airbnb! The room was clean, but simple. The apartment is very old, but in very nice location, within a 10 min. walking distance of Potsdamer Platz (many restaurants, shops, a casino and entertainment), Checkpoint Charlie and the amazing Topography of Terror museum, with a 200 meter preserved Wall. It is also near both U-Bahn and S-Bahn stations, so you can quickly reach anywhere in the city. I also strongly recommend using the Call-a-Bike service from DB, which allows you to rent bikes through your smartphone app. There is a station in front of the Topographie des Terrors.