If you're ever over in Berlin I'd recommend getting yourself to Kart Land - http://www.kartland.de
It was a €30 taxi ride from the centre and absolutely amazing, we did the Top Race 100 and had a whale of a time, basically you do 30 initial laps which includes warm up and then qualifying, and then the race itself is 70 laps, just the race takes around 35 mins so it's a great laugh, and these are top quality karts too, definitely the best I've seen since I was over at the Ralf Schumacher track with John, Andy, Zee, Ifraz and Gord, absoutely quality!