Well, you might have already done these, but:

Swiss Alps. My favorite is the Matterhorn (Zermatt), but others prefer the mountains above Interlaken. One of my favorite sights ever.

Fjords in Norway. I took the train from Oslo to Bergen, which is a nice ride, and then there's all kinds of stuff to do on the fjords once you're out there.

For more city-like stuff, I did really like Berlin and didn't spend enough time there. Also going to a tapas bar in Spain is fun and incredibly yummy. I also really enjoyed Lisbon, Portugal and environs.