Venice was cool as well--quite the experience only being surrounded by water. It's definitely the most confusing city I've ever been in--we got lost quite a few times. Our hostel was an old palace, so there were ornate wall hangings and paintings and canopy beds everywhere. Plus we got free breakfast AND dinner--a great deal. It's definitely the coolest hostel we have stayed in so far.
Florence was my favorite city in Italy...home to the world's best gelato, aka Grom and Gelateria de Neri. Per the suggestion of one of my friends who studied in Florence last semester, we went to Trattoria de Anita. Honestly, the best pasta I have ever eaten--the waiter worked his magic with the cook and let us have the famous truffle sauce, despite the fact it's not served usually at lunch.
Rome was great as well--we did a walking tour so we really got the history of the city. The Colosseum, the Spanish Steps, the
Roman Forum, the Vatican Museums, St. Peter's Basilica, St. Maria Maggiore....the list goes on.