What are some of the great places i should not miss whilst backpacking around Europe?

I am currently in my last year at school and am planning on backpacking around as much of Europe as possible during 2010 with a mate.

I don’t want to miss out on seeing some great attractions so i am asking for your advice.

Thanks heaps!

P.S. I love thrills and partying… but i want to see the historical stuff as well!