There are many charming squares in Rome with open-air cafes and restaurants and the loveliest of them is Piazza Navona. In the middle of the square there is the Fountain of Four Rivers. 

This tremendous, theatrical oval, dominated by the gleaming marble composition of Bermini’s Fontana dei Quattro Fiumi. The piazza owes its shape to an ancient stadium, built here in 86 AD by the Emperor Domitian, which was the scene of at least one martyrdom (Sant Agatha was thrown to her death for refusing to marry), as well as sporting events. Just to the north of the piazza, can you still see some remains of the original arena, sunk below the level of Corso Rinascimento. The piazza acquired its current form in the mid-seventeenth century. Its western side its dominated by Borromini’s facade for the church of Sant Agnese in Agone and the adjacent Palazzo Pamphili, built for Pope Innocent X in 1644-50.