The author of 'Basilica: The Splendor and the Scandal: Building St. Peter's' shares some advice for tackling the Eternal City.
Basilica of St. Peter
Climb up to the dome. The stairs will seem infinite, but if you persevere, you'll feel as if you've reached heaven. The views of the city, of the piazza below, and Bernini's colonnades are spectacular. You don't fully appreciate the colossal size of all those stone saints until you're standing beside them.
Since it's almost impossible to have a bad meal in Rome, there's no need to spend your euros in expensive restaurants. Trattorias are everywhere, moderately priced, and often family-run.
Romans have not sacrificed their afternoon siesta to 21st-century speed. Many smaller stores and churches close for a couple of hours in the afternoon. Be sure to check open hours.
Loll on the Lido
If you're suffering from an overload of lovely churches, art, and ruins, spend an afternoon on the beach at Ostia. It's a short trip from the center of Rome--you can even take a boat from the city--and the water is warm enough for swimming from May through October.
In a Pinch
Pinching posteriors is very Italian. Don't take offense if you feel a too-friendly hand. Instead, take it as a uniquely Roman welcome. Pinching purses, on the other hand, is a danger. Beware of ride-by grabs from thieves on Vespas. Tourists carrying shoulder bags are prime targets. Keep credit cards, cash, and passports in your pocket, money belt or fanny pack.
The Ultimate Gelato
One of the sensory delights of Rome is the ice cream. It's even better than the pasta. While my favorite flavor is espresso, the chocolate is also rich and dark, and the sorbetto (sherbet) is unforgettable. Two of the best-known gelato spots are in Piazza del Popolo and Piazza Navona. If more (blackberry) is in season, order a scoop for me.