We travel often and rely on Cruise Critic for advice and suggestions so I want to provide as much information I can to assist others.
We arrived in Rome a couple of days early and stayed at the Atlante Star Hotel. It was a nice hotel with free shuttle from the airport. Neither of us ever sleep on the plane so it was nice to be picked up by the hotel. The only problem was we had to wait about an hour for the shuttle bus. Hotel was nice, close to the Vatican and the breakfast buffet was excellent. We travel often and always carry on so we walked on cruise day across St. Peters Square and took the train from Roma St. Pietro Station to the port. It was probably a mile or so walk from the hotel to the train station.
We followed the instructions from CC and after leaving the Civit. Station walked about ¾ mile to the Port. (Thank you to all the CC contributors for directions) It was a very easy journey and the cost of the train trip was about 8 euros each. A bus picks you up at the port entrance and transfers you to the ship. We arrived at the port at 1:15 boarded about 1:30 and upon entering the ship they announced the cabins were ready. Nice surprise!
Cabin 1603 is very nice. Penthouse Deck Aqua Spa. Bed is near the bath. It is a bump out cabin with a slightly larger veranda.