What I love about Rome is the missing years between the fall of the Roman Empire and the Baroque. You can see the ruins of the ancient era, and you can see some seriously Baroque churches, but there are no Gothic churches. There are like a thousand missing years there, and the city is seriously living.
Did you see Ostia Antiqua? It's the old seaport, about a half-hour's train ride from Rome proper. It's wild.