The oval square was created in the 15th century, built on the site of the Stadium of Domitian from the 1st century AD.
In the center, in front of the church of Sant' Agnese in Agone by Borromini, is the Fontana dei Quattro Fiumi (Fountain of the Four Rivers) commissioned by Pope Innocent X, designed by Gianlorenzo Bernini and completed in 1651. The four figures represent the rivers Nile, Ganges, Danube and Rio della Plato.
At the southern end is the Fontana del Moro and at the northern end is the Fontana del Nettuno both designed by Giacomo della Porta in the 16th century. The statues of Neptune surrounded by nymphs were added to the northern fountain in the 19th century and Bernini added to the other statue of the Moor wrestling a dolphin in 1673.