Our first day at sea was spent cruising. Day two found us in either Pisa or Pompeii after docking in Naples.
On day three, we docked in Civitavecchia, Italy at 6 a.m.
Two hours later, our tour of the city left by bus, facing a one and 1/2 hour trip to the city from the docks (and a one and 1/2 hour trip back). (I just LOVE those early morning tours!)
Mainly, we drove past the sights that Rome conjures up, because the wait time to get inside the Coliseum, for instance, was 2 hours. (Only later, after our return, did I learn about the passes one could have purchased in advance that would have let you cut to the front of all lines, but they were primarily for 2 and 3 days, which would not have worked for those of us on an 8 and 1/2 hour tour of which 4 hours was spent on a bus).
After the extensive, exhausting trek through Pompeii (Day 2), the bus was quite welcome in the 100 degree heat. It was also very humid. 
I did some shopping with a fellow tour member, Deborah Matthews of Washington, D.C., and we were able to find a leather goods shop for souvenirs. We also tried the delicious dessert that our tour guide, Luisiana, went on and on about, calling us “my family” and using the phrase “you must know” to mean, “you should be aware that.”
I enjoyed seeing the area where the chariot races took place in “Ben Hur,” and the window from which a new Pope is announced. We were told by our guide that visiting the Treasures of the Vatican Museum would take at least a week and getting in to see the Pieta or anything in the Vatican requires extensive security, (plus, you have to be wearing something that covers both your shoulders and your knees.) Since my husband had on shorts, that was probably out in the first place.
I spent a period of days in Rome way back when, so the failure to be able to tromp around some more in 100 degree heat didn’t bother me at all.
Barcelona