The piazza takes its oblong shape from the first Century Stadium opf Domitian, site of sporting events and later cahriot races for the Campus Martius area. The Fontana dei Quattro Fiumi by Berninin represents the four great rivers (Nile Ganges, Danube, Plate). The horse representing the Danube was carved by Bernini himself. Statues are said to be shielding their eyes from the church built by rival Boromimi but the fountain was completed before the church.