As we move onto Rome, our first stop is Trevi Fountain. My suggestion here is to go as early as possible to avoid the massive crowds.
There are lots of good restaurants just down the street to the right of the fountain. Within an easy walk of the fountain, is the Roman Colosseum.
Pay for a skip-the-line guided tour, and make sure it takes you down to the floor, to experience all of the history. Right next door to the Colosseum, is the Roman Forum and Palatine Hill.
Again, a guided tour will give you the back story of how this appeared back in the day. Lots of history to be experienced.