Within this central arch is a grand doorway, the stilted semicircular arch of which is of three orders, the central plain, the others covered with carvings. The piers supporting the main arches have tiers of shafts in two heights; the lower tier corresponding in height with those of the doors pierced within the arches, and the others, which are smaller in diameter, and more numerous than those which support them, rising to the springing-line of the main arches. The side doorways have very Eastern-looking arches, the semi-circular line being carried on nearly to the centre, and then turned up into an ogee. These and some other portions as, e.g., the windows over two of the doors, and the pinnacles between the gables, belong to the fourteenth century, whilst the finish of the gables themselves--great ogee crocketed gables with figures at the apex of each--is probably of the fifteenth century. All these archways open into the cloister, or narthex already mentioned. Here, where the roofs still glow with the most precious early mosaics, and the walls with marble, either used as inlays or for shafts, one gets a first and not unworthy hint of the beauty which awaits one in the interior. And then, on entering the nave, the deep tones of an organ are heard reverberating through the old building; many people kneel devoutly at their prayers around us; the hot glare of the sun has gone, and in its place a cool, quiet, dim light reveals the whole magnificence of the design. It is quite in vain to describe this in formal architectural terms. The colour is so magnificent that one troubles oneself but little about the architecture, and thinks only of gazing upon the expanse of gold and deep richly-tinted mosaic all harmonized together into one glorious whole. The mosaics commence throughout the church at the level of the crown of the main arches dividing the nave from the aisles, and are continued up the remainder of the wall and into the domes; even the angles or arrises of the walls and arches are covered with gold mosaic; so that all architectural lines of moulding are entirely lost, and nothing but a soft swelling and undulating sea of colour is perceived. There is nothing violent or garish in all this profuse decoration. The gold mosaic, used as it always is in early works, set irregularly in, and surrounded by a white line or joint of plaster, is never conspicuously bright; the drawing of the figures and subjects may be criticized, but at any rate it is always direct, simple, and intelligible, and the colours of the draperies bright and harmonious, whilst the arcading and wall-lining which fills the lower part of the walls is all of marble, which has now a rich, warm, but quiet tint, singularly suitable as a base to the more gorgeous colouring of the upper part of the walls and domes.