It was a nice experience to stay at Katharina's apartment in Berlin. The location is great as one can reach both the U-bahn and the S-bahn with 2-3 minutes walk. Also, parking is free in the nearby streets. There are many small fast-food restaurants and supermarkets closeby, so food is not a problem. The apartment was clean and cosy, it is perfect for 1-2 people. There is no street noisy at all as it faces a little courtyard. Neighbours could be heard, especially kids from upstairs, but they were luckily quiet at night. I felt a bit cold sometimes, but when I called Katharina, she adjusted the heating (they control it from their own flat). My only problem was that I found the towels pretty hard/rough, so if you like fluffy soft ones, better bring your own. Other than that, it is a great place to stay in Berlin and it is especially safe for solo women.