Where to go in the Netherlands?

In The Netherlands, go to Rotterdam! It was one of my favorite cities. The area was bombed heavily in WWII, and they rebuilt using a lot of cubist and other wacky architecture. Rent a bike, no matter how cold it is, and bike over the large bridges and then out to the deep water port. Rotterdam has the largest deep water port in Europe.

Have fun!

Is an answer to your question still useful (ie, you’re not already visiting)?
Such a small country, so many things to see. I can give you some ideas, but that’ll depend on what you like.
Amurph has a nice suggestion, but do look up where to find that architecture (eg, the cubist houses), before you’re peddling all over Rotterdam.
Other places are Delft & Leiden, which preserve some of the classic Dutch ‘Golden Age’ city centers (Amsterdam does too, but too many tourists there, and too big. Delft & Leiden are also closer-by to Rotterdam).
A bicycle is definitely a must try: rentable at practically every train station, and various other places. Just beware of the tram tracks ;-) !