Ave Roma Immortails, Volume 2 by F. Marion Crawford

There used to be a tradition, wholly unfounded, but deeply rooted in the Roman mind, to the effect that the great bronze pine-cone, eleven feet high, which stands in one of the courts of the Vatican, giving it the name 'Garden of the Pine-cone,' was originally a sort of stopper which closed the round aperture in the roof of the Pantheon. The Pantheon stands at one corner of the Region of Pigna, and a connection between the Region, the Pantheon and the Pine-cone seems vaguely possible, though altogether unsatisfactory. The truth about the Pine-cone is perfectly well known; it was part of a fountain in Agrippa's artificial lake in the Campus Martius, of which Pigna was a part, and it was set up in the cloistered garden of Saint Peter's by Pope Symmachus about fourteen hundred years ago. The lake may have been near the Pantheon.

No one, so far as I am aware, -- not even the excellent Baracconi, -- offers any explanation of the name and device of the Ninth Region. Topographically it is nearly a square, of which the angles are the Pantheon, the corner of Via di Caravita and the Corso, the Palazzo di Venezia, and the corner of the new Via Arenula and Via Florida. Besides the Pantheon it contains some of the most notable buildings erected since the Renascence. Here are the palaces of the Doria, of the Altieri, and the 'Palace of Venice' built by Paul the Second, that Venetian Barbo, whose name may have nicknamed the racing horses of the Carnival. Here were the strongholds of the two great rival orders, the Dominicans and the Jesuits, the former in the Piazza della Minerva, the latter in the Piazza del Gesu, and in the Collegio Romano; and here at the present day, in the buildings of the old rivals, significantly connected by an arched passage, are collected the greatest libraries of the city.