You may go to Piazza Navona for its famous fountains, to visit the church of Saint Agnese(Sant’Agnese in Agone), for the story of the rivalry between Bernini and Borromini the artists who put their mark here. Also for the Palazzo Pamphili with its frescoes or Palazzo Braschi where Museo di Roma is. Btw there’s an photographic exhibit on the subject of Nino Manfredi, until 6 January 2015, Nino! the one who Romans love.
You may go in the summer to watch the numerous painters displays around the fountains, on the oval circomference, listen some street music(more or less Italian) or eat at the Vacanze Romane or some place(there are lots), enjoy the view, people, statues, architecture and begging pigeons and seagulls. You may sit on the edge of a fountain, eat your ice cream(number of gelaterie in rione Parioli, ie neighborhood) and take a selfie.
You may go on winter holidays when there’s this huge fair with marzapane, pannetone, red glazed apples, panini with porchetta, Christmas ornaments, sorcerers riding brooms(La Befana or Epifania is on 5 January’s eve, when every well behaved child gets sweets but the others only charcoal; there’s some black candy named carbone). You may have your selfie with Babbo Natale or ride a merry-go-round…mmm, maybe if you’re five or so. And if you’re at the wrong time you may find yourself blocked in a crowd resolved to have the time of their life in Piazza Navona. One meter in a quart of hour; it’s called experience and I have it 🙂
So you should definitely go in Piazza Navona. With a camera…