A new world in a city!
Berlin is a city from the very first world. It's well planned and developed. You'll be able to go everywhere by metro. And, the most important thing, it's one of the best places to get to know about the 2nd great war.
Insider Tip:I recommend to get the free walking tours around the city. The guides usually pass by in front of the hostels to pic you up. They are really good and worth it!