The first time we cruised to Florence and Rome we did the ships excursion called ‘Rome on your own’ and the same to Florence. Basically you are taken into the city and then you wander on your own and meet back at a prearranged time. This is cheaper than a guided tour and you have the security of knowing the ship will wait for any delays. Since then we have caught the train independently and just allowed plenty of time to return. On one cruise the ‘Rome on your own’ passengers were on our train so we knew we were safe. Same with the ferry to Capri. If you catch the same ferry as the tour group, make sure you take the next to last one back as the tours usually catch the last ferry.