Favorite Piazza in Rome?

Piazza Navona - late at night especially if there are street performers. Piazza Santa Maria in Trastevere - before dinner, sitting at a cafe just enjoying the people and some street performers. Piazza della Rotunda - any time. No matter where I continually remind myself: I deserve this! Enjoy!!!!

The best ones are smaller ones near your hotel, or "home".

For example, we have stayed several times at a hotel in the Trastevere. Nearby was the Piazza de Santa Maria, good activity, nice cafes, bars and restaurants, even mix of tourists and locals in the evening, not to mention a nice Cathedral and a statue in the center. Just as nice though, just behind our hotel was the Piazza di San Cosimato, not really much at all, but a few restaurants and bars, a playground, a market in the morning, and almost all local; very pleasant to just sit in for morning coffee or an evening glass of wine.

We probably would not have traveled across the city to just go to these places, they were near our hotel, usually we would stroll through in the morning or evening, I think any stress to get there in the morning or get back to your room in the evening would have killed the "chill" you gained. So once you find a hotel, search for places near there.

Good advice above; I'll add that to people watch try the Piazza del Popolo (and consider walking a couple blocks north to go to the local community center) but to do some walking away go to the Terrazza Gianicolo and the Villa Pamphili, assuming the weather cooperates.

I should have mentioned that we have an apartment for the week in Trastevere. Thanks for all of your great recommendations!

My favorite Piazza's are two with fountains: 1. Piazza Navona- Fountain of the Four Rivers. I love everything Bernini. The piazza is especially magical at night. 2. Piazza Mattei- The Fontana delle Tartarughe. I love the turtles that were added. They look very realistic. Every time I've seen this unique fountain it surprises me. Many may recall that the fountain appeared in the 1999 film the "The Talented Mr. Ripley."

Oh, if you're there in Trastevere already then definitely get fixins' for a picnic and go get lost in the park west of the Villa Pamphili.
You can easily join a pickup soccer match, or just cheer them on with a toast from your bottle of crisp white wine. Consider something from Orvieto. Cheap, but tasty and refreshing.
There's also a dog park, if you're missing your own pooch.

My favorite Pizza in Rome is the thin-crusted Roman style.
Oh, piazzas, well I like to eat my pizza at Piazza Navona.

A lot of the Piazzas are beautiful and have their story to tell -

My most favorite is Piazza San Pietro.
Second in line is Piazza Navona.

Navona, Santa Maria in Trastevere, the one in front of the Pantheon, and the one in Monti (forgot the name, looking at a map is it Madonna Della Monti?)

Mira, Piazza Della Rotonda (The Pantheon) is pretty too.

Yes, I guess I will add that as third favorite since that too holds a special memory.

My favorites (in alphabetical order):
Piazza del Campidoglio
Piazza Navona
Piazza San Pietro
Piazza di Spagna
Piazza Venezia

The first 4 are special because of their beauty.
The last one because of the “balcony” from where Italians heard the speeches that inspired so many political leaders with strange hairdos, even orange ones.