This is the outfit I ended up in for a five-hour tour through the Colosseum and all of Ancient Rome. It was light and breezy and gave minimal tan lines, so all was well for me. After our tour, we trekked down the river to peek through the keyhole at Aventine Hill (totally worth it) and then took the Metro back home before a late dinner at a restaurant I don't remember the name of in Pigneto, flirty Italian waiter and all. Every day here is more paradisiacal than the next.
I highly recommend a tour guide for the incredible historical sites in Rome. Even if you have been to the places and seen the sights, the detail and insight a guide provides has been invaluable (plus you get to skip all the hour-long lines at every entrance!). Through Eternity hosts exceptional tours and both guides we experienced (Cinzia for the Vatican, Luca for Ancient Rome) were engaging and vastly knowledgeable.
I still can't believe I'm posting this from a rooftop terrace in Italy.