I've been to
Sweden - boring
Germany - boring, I wasn't in berlin though, hear it's exciting
London, England - great!
Spain - hot, boring
Praha, Czech - kinda hot, great if you're 14 xD
Amsterdam, Netherlands - A lot like Copenhagen in Denmark. Cozy place with some decent museums and a nice pace. Great if you're young and like to go out.
Dublin, Ireland - BORING! There are no pretty people in Ireland, NONE! They are VERY religious.
Greenland - Cold <3 Greenland is an experience. The weather is cold, but not really that cold since the air is so dry. There's no nightlife. People there still live in a somewhat "nature-environment" (barbarians) which is interesting. The food stinks. You eat fat from whales and canned food. Fresh food costs 3 times what you'd find in your own country, however, as it gets older, the price drops day by day with roughly 1$ a day.
Recommend! London if you're into "big" city life, or Greenland if you're more into nature and rock climbing and dogsledge and such.