Originally Posted by
bonfire00
We were there last summer and there was this little train that just ran from the docks into Rome, it was walking distance from the ship. You'd have to try and google it, as I don't remember the name.
It is the Rome Express
http://www.seatrain.biz/ that will take you to Roma San Pietro station near the Vatican.
Check the website to know more. It used to be sold only on board for packaged excursions. It is an alternative anyway.