Piazza Navona is a public space/plaza in Rome, Italy. It is built on the site of the Stadium of Domitian, built in the 1st century AD, and follows the form of the open space of the stadium. The ancient Romans went there to watch the agones , and hence it was known as "Circus Agonalis" . It is believed that over time the name changed to in avone to navone and eventually to navona.

More details: https://en.wikipedia.org/wiki/Piazza_Navona