I came to Rome yesterday. Bus to Napoli from Agerola and train from Napoli.
I walked all day today and saw a lot of famous things. Started with Colosseo and moved to Fontana de Trevi, Panthenon, Castel S. Angelo, and Vatican city. Also other famous piazzas. As you can see in the pictures, the weather was fine. Colosseo and Vatican was super busy with tourist and I couldn't be bothered to wait in the queue. The queue for Vatican was so long that I didn't even think about waiting for it.
It's not close to each other but the famous sites in Rome isn't a non-walking distance. Maybe it's easier to walk because it's like connecting the dots by walking.
I saw the major places today so I might go to a park tomorrow and maybe, if the queue is not too bad, I'll enter Vatican.picture: above, Colosseo. below, Arco di Costantino, next to Colosseo