I'm supposed to be gardening, but..
My favorites (I won't list my skips, we're all different with places we most appreciated, and that's a sign of the richness..)
I can't remember if you're been to Italy before, Mac - I'm thinking so but not sure.
Anyway - Rome:
* Four churches - out of many -
Sant'Andrea del Quirinale
- by Bernini
San Carlo Borromeo
- by Borromini
They're adjacent, with S. Carlo being at the intersection of via Quattro Fontane and via del Quirinale - not far from Piazza Barberini, walking.
Two jewel boxes of distinguished architecture. Be aware churches are often closed at siesta time, and open after it.
Santa Maria del Populo
- with a Rafael chapel and a Caravaggio, a loved old church on the pz del Populo. Might be a miss, since it is recently part of the Dan Brown da Vinci code hoohah. I'd substitute then some of the other churches with Caravaggios.
One that was hard for me to get into, only open at some odd times - Sant' Ivo
by Borromini. Totally elegant..
Oh, wait, a fifth, the church built over a church over a mithras temple, San Clemente
And, oh, sixth, I enjoyed the church right by the Pantheon, Santa Maria della sopra Minerva
(built over temple to Isis).
*Favorite building/favorite spiritual place - the Pantheon/the Pantheon in the rain
*Favorite gallery by far - Galleria Doria Pamphilj - best to go at earlyish morning, it closes (chiuso! chiuso!!) at 1 pm. I doubt it's open after siesta, not sure
* Favorite pizza - at a place called La Focaccia very near the entry to Sta. Maria della Pace.
* Favorite gelato/pastry/coffee place - Giolitti, on via di Uffizi Vicario. Tucked in a small street by pz. Montecitorio, follow the people coming at you with ice cream cones. The street is on some but not all maps. ( the big expensive more finely tuned ones.
Many other gelato places.. The Frugal Travel has a favorite, back with a link on that later.
* Favorite piazza - Piazza dei Mattei, in the ghetto area, great to find it by surprise, has a splendid fountain featuring turtles..
Well, that vies with Campo dei Fiori.. and I guess C. dei Fiori wins. Go in the early or mid morning..
* next favorite - Pz. Navona, early morning..
* next favorite - Piazza San Pietro, by Bernini, in front of St. Peter's. I strongly favor seeing it for the first time NOT by walking down via Conciliazione, where you face it head on for some blocks, but from the side streets, where the place is a "surprise" after walking through the great columns. This is easily done if one takes the metro and gets off at the Ottaviano station.
* Favorite food - the antipasti at many restaurants; carciofi alla romana; carciofi alla giudea, pizza (the one previously mentioned, and another at Pizzeria Archetto called "pizza vesuviana" - arrives at table puffy and steaming, filled with scrambled eggs and (stuff).
Hard to say about restaurants. Being me, I've done scads of research before my trips - and ended up eating at what was nearby when I/we were hungry.
That said, I'd avoid a lot of restaurants near tourist sites with tourist lists of dishes showing in the menus that are usually placed behind glass at the front of restaurants/trattorias. I think it's smart to familiarize yourself with some names, in case you end up nearby one of them when you're hungry.
Consider looking these cities up on Chowhound. Venice, for example, has been famed for not great food, but I've read about some wonderful places there - but don't have the names saved. Wonderful not being the same as expensive, at least necessarily.
Enough for now..