Venice:

Favorite place I have ever been. Weather was beautiful while we were there. Loved sitting in Piazza San Marco and having drinks while listening to the orchestras. Drinks were extremely expensive, though. The Rialto Bridge, Basilica, and Doge's Palace where all really cool. We also headed to the islands of Murano and Burano while there. Got to see the glass blowing and the cool colorful houses.

Pisa:

We were originally scheduled to go to Pisa, but audibled to Siena, which was awesome.

Florence:

Uffizi is a must. Try to get into the Vasari Corridor. Really neat and hard to do. It exits into the Boboli Gardens, which are beautiful. Basilica of Santa Croce is really cool. Tombs of Dante, Galileo, Machiavelli, and Michelangelo. The actual statue of David is in Galleria dell'Academia. Skip it. Line is huge and it is the only must-see thing there. There is an exact replica somewhere else in the city. Donatello and a lot of Medici are buried at Basilica di San Lorenzo. Worth swinging by if you are chasing Ninja Turtle tombs.

Rome:

Rome is cool, but it is A LOT more spread out than the other places, so seeing things in a timely fashion is very difficult. An under the radar thing to check out is Santa Maria della Concezione dei Cappuccini, which is a church made of skulls. Vatican is an absolute shitshow. If you are claustrophobic in the slightest, you will have a panic attack on the way to the Sistine Chapel. St Peter's Basilica was much less crowded, though. Coliseum, all the fountains, Villa Borghese are all cool spots, as expected.

You will be swarmed by migrants trying to sell selfie sticks. It gets really annoying and kind of takes away from the luster. Really bad in Venice, Florence, Rome. Didn't see as many in Siena or Orvieto, which leads me to believe that you won't have as much of an issue in the smaller towns.