Cramming for Italy

My wife and I set out across the Atlantic tomorrow for a few days in Italy. We'll be flying into Venice, before moving on to Florence, Pisa and Rome. I've been voraciously reading about these three cities in hopes of remembering some of the sites we will visit. The famous ones are easy, but there's so much history in Europe I'm a little overwhelmed. I'm not worried, though. We have a long flight ahead of us -- plenty of time to finish cramming.