where to go for a city break?

I want to take my girlfriend away to a european city, I am thinking April sort of time, but where to go? We are both 21, we would like nightlife but more restaurants and bars rather than nightclubs, but i also want a sort of picturesque city with a lot to do, price is a factor as well, does anyone have any advice? I was thinking maybe Rome, Milan, Dublin but if anyone has any other opinions that would be brilliant. We will be flying from London or Birmingham and only going for 3 nights.