March, 2006 stayed at the Ritz Carlton in Berlin. It is right across from the Potsdamer Plotz. Centrally located. Easy to walk to all the sites. We stayed on the Concerg. floor. Rooms are beautiful. Staff at hotel are great. Someone recommended we take the double decker bus, which has a stop right near the hotel. You can get on and off at museums, attractions, etc.
I would highly recommend this hotel. Do not miss the Pergamon Museum and the Egyptian museum. Other great museums; can't remember names.
Have fun.