"The most extensive hall ever constructed by human art expands in magnificent perspective before you. Advancing up the nave, you admire the beauty of the variegated marble under your feet, and the splendour of the golden vault overhead, the lofty Corinthian pilasters with their bold entablature, the intermediate niches with their statues, the arcades with the graceful figures that recline on the curves of their arches. But how great your astonishment when you reach the foot of the altar, and, standing in the centre of the church, contemplate the four superb vistas that open around you; and then raise your eyes to the dome, at the prodigious elevation of 440 feet, extended like a firmament over your head, and presenting, in glowing mosaic, the companies of the just and the choirs of celestial spirits.... "Around the dome rise four other cupolas, small, indeed, when compared with its stupendous magnitude, but of great boldness when considered separately; six more, three on either side, cover the different divisions of the aisles; and six more of greater dimensions canopy as many chapels. All these inferior cupolas are, like the grand dome itself, lined with mosaics. Many, indeed, of the masterpieces of painting which formerly graced this edifice have been removed [to the Church of S. Maria degli Angeli, see page 265], and replaced by mosaics, which retain all the tints and beauties of the originals, impressed on a more solid and durable substance. The aisles and altars are adorned with numberless antique pillars that border the churches all around, and form a secondary order" (Eustace). The variegated walls are in many places ornamented with festoons, wreaths, crosses, and medallions representing the effigies of different pontiffs. Various monuments rise in different parts of the church, of exquisite sculpture, and form very conspicuous features in the ornament of this grand temple.