We spent a few days in Berlin recently and stayed at the Westin Grand, which is near to number one on the linked map: www.visitberlin.de/sites/default/files/weihnachtsflyer_en-web.pdf Walking distance to most places, especially the Brandenburg Gate, Holocaust Memorial and the Reichstag building.
Yes we've had a few days in Berlin and the Christmas markets. Thoroughly enjoyed it. Try the afternoon tea in KaDeWe - divine. We also ate in a restaurant that had been in East Berlin down from the arch I can't remember the name but it is original Art Deco not touched that was also a lovely experience. I adore Berlin.
We only did a day trip, which was surpringly cheap . Don't miss the bid stores KaDeWe and Peek and Cloppenburg. Also Alexa , a mall with over 180 shops.
KaDeWe (Kaufhaus des Westens) is unique , it's 6 floors and the top is all about food ! At Christmas it's fabulous .