Good day trips to Europe?

[montecristo]

What are some good day trips to Europe? Other than the obvious ones like Paris or Rome.

This year, I went ot Krakow (which was alright, but ran out of things to do before the 9pm flight back) and Bologna (loved it). I am tempted by a day trip to the Parthenon, although that may be cutting it fine.

PS This is not the thread for opinions about how you need at least three years to see Florence or Vienna properly.

[hoegaardenruls]

Bruges is a good one by car, with a cheap tunnel crossing, otherwise (if flying) how about the likes of Berlin, Geneva or Zurich?