Created between the late 16th and early 17th centuries based on a design by Domenico Fontana, it saw the collaboration of masters such as Michelangelo Naccherino, Pietro Bernini, and Cosimo Fanzago. Moved several times over the centuries, it displays a rich Baroque iconography. At the center, the statue of Neptune with his trident stands on a rock populated by nymphs, tritons, and sea monsters spouting water. The large outer basin is decorated with lions holding the viceregal and city coats of arms.