Berlin is good fun.
Belgrade looks really nice and probably isn't too expensive...
I want to go to Sarajevo but I'm pretty sure Bosnia isn't the best place to hang out yet.
I just came back from 2 weeks travelling the balkans, we spent 2 nights in belgrade, then to sarajevo for 2 nights, we loved it, travelled to another place in bosnia called mostar, very beautiful countryside. Then, we were supposed to go to monenegro, but we liked sarajevo so much, we went back and stayed another 6 nights there. My third favourite city in the world, its awesome. They have rejected western culture, so if you are looking for high street shops, mcdonalds, kfc, starbucks, then you will be sorely dissapointed. If you are looking for a city with plenty of local food and bars, where muslims, catholics and orthodox have an equal share of the population, creating a strange but very relaxed and friendly culture - then sarajevo it is!
I think it was in the top 10 lonely planet places to visit in the world last year, which I took with a pinch of salt but once I arrived there...
I dont think I have felt safer or been in such a friendly place in my life. This surprised me even more when you learn about its recent history.
I miss sarajevo
There is also lots of romantic countryside to visit, like a massive road lined with trees that used to be franz ferdinands palace and plenty of out of the way springs and waterfalls.
Although be careful taking your girlfriend, make sure you wear sunglasses because the girls there...