The four columns are 20 metres or 66 feet high. The base and capital were cast separately and the shaft of each column was cast in three sections. Their helical form was derived from the smaller marble helical columns once thought to have been brought to Rome by the Emperor Constantine from Solomon's Temple in Jerusalem and which were used in the Old Saint Peter's Basilica (See the article Solomonic column). From the cornice hangs a bronze semblance of the scalloped and tasselled border that typically trimmed the papal baldacchino. The structure is decorated with detailed motifs including heraldic emblems of the Barberini family (Urban VIII was born Maffeo Barberini) such as bees and laurel leaves. The underside of the canopy and directly above the officiating pope is a radiant sun – another emblem of the Barberini – within which, devout Christians believe, the Holy Spirit dwells.