Berlin is awesome amazing and really big if the biggest city you have ever visited is Rotterdam, and the smallest town in Holland, Persingen, is within 15km of you're home. It was impossible to visit all the of the sightseeings, so we had to make a selection and planned pretty much all of it.
We visited the KaDeWe, Berliner Dom, the Pergamon, the Jewish Museum and climbed up the Siegessaüle. Not that much looking back to it, but you don't quite have to visit every museum to be impressed and amazed. Outside there's a lot to see and to do.