As I was in the area late last night, I wandered by the new Alexa shopping centre which was supposed to be opening at midnight. I was expecting it to be busy - electronics superstore MediaMarkt has been splashing its heavily discounted opening offers over the whole of Berlin for the last couple of weeks - but I wasn't expecting the crowds to be backing up across the street to Alexanderplatz (the police had even cordoned off part of the road). The picture on the right (click to enlarge) shows what it looked like just before midnight, and this is a video from someone who made it inside:

According to this eyewitness report (German) they had to close the place at 1.30am.