What are the best "hidden gem" cities in Europe?

I'm looking for a few cities to visit that are not too touristy. I have a 2 week vacation in April 2010. I love historical monuments, natural scenery, shopping, and just wandering around the streets and relaxing at a cafe. I've been to France, Italy, the UK, Monaco, and Luxembourg, and would now like to travel a bit further east. Any ideas/information would be great! Thanks!