I believe you need to put yourself in a certain mindset before making a trip to Berlin. It's not a beautiful city—in the traditional sense—and walking around the city can be very grim. However, the history and artwork displayed in many Berlin museums is worth the trip. My two favorites were the Deutsches Historiches Museum and the Pergamon Museum.
A living map of Europe “occupies” the lobby floor: the morphing boundries of the German empire over centuries is projected onto a map of Europe. The display is a brilliant means of simply conveying the evolving history of power.
The museum is layed-out logically. Walk through the second floor, which will deliver you from 1 BC to 1918, then descend to the first floor to take-in 1918 to the present. You’ll learn a lot, and some of the images (none exactly cheerful) will stick with you for awhile.
What to do for Fun in Berlin: http://bit.ly/18OBQPT