Berlin is a beautiful city.These are a few places that I would suggest --
Brandenburg gate
Belin Zoo
Potsdam and Sansucci Palace(this would be a day trip.the palace is amazing and the boat ride to reach Sansucci is thoroughly enjoyable)
Shopping at KADEWOO(the largest shopping place in Europe)
Site where the Berlin Wall existed.
City tour(take one which includes former East Berlin)
Hope you have a wonderful trip.
Regards,
Vpas
