These are the medieval gates to the city. They were not used in Caesar's time but much later and are on the edge of the city near the subway station. The subways in Rome are rather pointless because they are on the edge of the city. Anywhere in the middle of the city they try to dig they find something importnat and it becomes an archeological dig and the line can't be built. The Roman subway is infamous for its pickpockets and as I stepped onto the platform of the train I felt someone pullling my sunglasses out of my pocket so I grabbed them and shoved them back in. there were a couple of shady people who could've done it but can't prove anything.