YTes - beong so close to Amsterdam Rotterdam often gets overlooked as a destination. I have been there for the christening of the Eurodam. It is a nice city but not with the same charm as Amsterdam, obviously.
I have been along the Iberian Coast, mostly I enjoy the ports in France, Gibraltar, etc. I am not a big fan of Lisbon. I spent two weeks there once when I was on Statendam during dry dock. Not much to do.
I just saw Valencia, a very interesting place. I really like how even marginally large towns in Europe will have a subway system and a busy downtown area. So much a better culture than our American car culture.