Martin's place is located within two minutes of the U bahn. It is more than enough room for 3 people and it is very cozy with everything you need for a short trip to Berlin.
Martin is also great. He met us at the apartment to let us in. He was flexible with the times due to our early train. He showed us everything we needed to know about the place and gave tips for getting around in Berlin and tips for things to do.
We would stay here again.