Martina has a real nice place. It's in a quite a busy neighborhood, but the flat is very quiet and offered every convenience we needed. Martina met us personally when we arrived -- a nice gesture. She oriented us to the apartment, and also gave us many tips about Berlin and the immediate neighborhood. We spent most of our time doing typical sight-seeing around Mitte (Reichstag, Museum Island, etc.) Kreuzberg (specifically Kotbusser Tor) is a very vibrant area (almost overwhelmingly so). There are more nice restaurants within a single block than we could have experienced in twice the time we had during our trip. It was a nice spot to unwind over dinner after a busy day.