"The diameter of the cupola is nearly equal to its height. The round aperture at the top, by means of which the interior is lighted with a magical effect, measures about twenty-eight feet in diameter. Here is still to be seen the last and only remnant of the rich bronze decorations of which this edifice formerly boasted. It consists of a ring, adorned with eggs and foliage, encircling the aperture, and not merely strengthening the edge of the wall, but constituting a graceful and at the same time a simple and judicious ornament. "It is certain that the five converging rows of gradually diminishing cassettoni have been decorated in a similar manner, and it is stated that vestiges of metal were discovered during the process of whitewashing. "The six niches between the altars are each supported by two fluted pillars and a corresponding number of pilasters, the greater portion of them being composed of monoliths of that costly yellow marble frequently employed by the ancients. They are more than thirty-two feet in height, and, as regards size, are unique of their kind. It has been impossible, even for the ancients, to erect, of this rare material, all the pillars required for the embellishment of this splendid edifice, for which reason they were obliged to substitute six of pavonazzetto. These, however, they stained, without injuring the brilliancy of the marble or the transparency of the grain, in such a manner as to bring them into harmony with the other yellow masses, and to deceive even the most practised eye. This circumstance is of great importance in forming an opinion on the coloured architecture of the Greeks, as it shows how they contrived to harmonize the white marble masses without concealing the texture of the noble material. "It is stated by Pliny that caryatides were placed here by a certain Diogenes of Athens, corresponding to the pillars which support the architrave. "Apparently they were a free repetition of the caryatides of the Pandrosium; and probably the statue in the Braccio Nuovo, which was brought from the Palazzo Paganica, in the immediate neighbourhood of the Pantheon, was one of these, the scale being precisely adapted to this situation. "Some of the large nails used in riveting the bronze plates together are still preserved in the different museums. We are indebted to Serlio, an architect of the sixteenth century, who preserved a drawing of it, for the only information we possess concerning this ingenious piece of mechanism. The Pope mentioned above, a member of the Barberini family, had the barbarity to carry off and melt down these important remains. An inscription on the left of the principal door celebrates the judicious transformation of these masses of bronze into cannons, and ornaments for churches" (Braun).