Got a couple of hours in Berlin?
Start outside the Pergamon Museum. Enjoy the sculpture in the gardens and Alte National Gallery. Walk to the National Gallery. Sculpture outside there ditto.
Cross the Spee and walk down Under den Linden (speed up passed the boring bits) to the Humbolt University. Check out statues, sculpture and books in its forecourt.
Cross the road and stand outside the other part of the University in the square where the Nazi's burnt the books in May 1933. Find the perspex covered underground memorial of empty bookshelves for the same. Contemplate history for a bit.