Oh the History!
Berlin is an absolutely amazing city with an incredible history that you feel every moment you're there. There is so much to see and do in Berlin that it is the first city I've been to where I feel like I can go back for another 5 days and still have plenty to do. Berlin really has great value for the money as it offers everything a major city would (great transportation, international cuisine) but at a fraction of the price compared to Paris/London. This may be my favorite city in Europe.
Insider Tip:Plan at least 5 days in Berlin. I thought that was crazy when I read it before hand but I stayed for 4 days and hardly scratched the surface.