Gerhard is SUCH a great host. He went out of his way to help me, even lending me a laptop as I had some problems with mine in the first couple of days and was in Berlin to work. He gave me a wealth of tips for places to see, walks to do etc. etc. and I knew I could contact him at any time. The apartment is really conveniently located - a few minutes' walk from the Julius-Leber SBahn station and you are in very central Berlin in minutes. Lovely apartment in a pleasant area which still has the feel of authentic Berlin.