The intervention involved the colonnades of the seventeenth-century square designed by Bernini. The colonnades, made in three lanes, with 284 columns of the Doric order and eighty-eight pillars in Tivoli travertine, are joined by a very simple entablature but crowned by a series of 140 statues of saints 3.10 m high, and by 6 large coats of arms of Alexander VII Chigi.