I've been to Pisa, Italy as well. The great thing about Pisa is that it's only an hour train ride from Florence. And because Pisa is such a small town with very little to see (it's all right here), you can do it in a day or less. ;)
Prague, we were here for New Years '11-'12. One of the most amazing experiences of my life. The crowds and fireworks were unlike anything I had ever experienced. I even hit the clock tower on the left of the photo once or twice with bottle rockets.