Andrea In Rome I'd recommend checking out Michelangelo's Moses. It's up a hill close-ish to the Colosseum and it's an incredible statue. I got to see it 18 years ago (yikes!) on a field trip when I was studying in Rome and the professor explained that the look on Moses' face appears to change depending on the angle that you look at it. From one side, he's angry and when you walk to the other side, he just looks absolutely devastated. I think my jaw was on the floor the entire time I was observing it! There are also a fair amount of other historically significant relics in the basilica.
Two things to note: The hike up the hill can be a bit intense depending on your mobility. Also, as with almost everything in Italy, the basilica in which it is located could be closed at random. I tried to take my ex there 7 years ago and we ran into that problem. Maybe book a tour that includes the basilica? Or just enjoy the adventure!
Enjoy Europe!