Depends on how much money you have and how one plans to travel from site to site.
Greece, Britain and Hungary/Romania are the best for various reasons; France, Germany and Italy have a great deal to offer. Britain is expensive; the other two harder to get around. I'd go to
Budapest and work from there into Transylvania and take the train to Austria or Greece.
hanks for asking.
I adore Italy and France. Especially Italy. Florence, Venice, Rome, ... <3
Austria is really beautiful, there is a lot to see and do. Prague, Czech Republic is amazing too! I highly recommend both of those :)
Portugal, is good city and people! Perfect place, and chipp!! XD