If you have only a day in Rome, I would tell you to enjoy a few sites. Start with the beautiful Piazza Navona for some food and people watching.
Continue on your way but be sure and stop for a delicious gelato (chocolate is always a favorite choice). Afterwards toss a few coins into the Trevi Fountain for good luck then see a major ancient Roman site, the Pantheon. Its enormous and shouldn't be missed. After this you can spend the rest of your day shopping....bellisimo!
My top five list for a day in Roma:
- Piazza Navona
- Trevi Fountain
- Piazza di Spagna
- Via Condotti shops