We got off at Termini, the railway station is huge and it takes alot of time to get out from there - the train from Civitavecchia stops far away from the entrance.... and of course on the way back (after you have managed to see some of Rome which is chaotic, full of people and very hot in summer) you will have to be back on the train in time not to miss your cruise ship and again it is exhausting getting back to the ship.
There are many shops in Termini and you can easily spend there lots of time just looking at things and people and not get bored.

