Although we only spent two days in Rome, my highlights there included:
The Colosseum-even if you just walk by and see the outside. The enormity of it is mind-boggling.
The Pantheon-the best preserved ancient monument and one of the most influential, architecturally speaking.
The Neighborhoods-just walking from one part of the city to the next really is the best way to experience it.
The Vatican-if you can swing a private or semi-private tour, it makes the experience so much more enjoyable.
Gelateria Millennium-near the Vatican; some of the best in the city.
La Buvette-we had a great meal there.
I will post about Florence and Orvieto very soon.