[Illustration: FIG. 159.--CHURCH OF SANTA SOPHIA AT CONSTANTINOPLE. LONG SECTION. BUILT UNDER JUSTINIAN BY ANTHEMIOS AND ISIDOROS. COMPLETED A.D. 537.] A church which had been erected by Constantine, dedicated to Santa Sophia (holy wisdom), was burnt early in the reign of Justinian (A.D. 527 to 565); and in rebuilding it his architects, Anthemios of Thralles, and Isidoros of Miletus, succeeded in erecting one of the most famous buildings of the world, and one which is the typical and central embodiment of a distinct and very strongly marked well-defined style. The basis of this style may be said to be the adoption of the dome, in preference to the vault or the timber roof, as the covering of the space enclosed within the walls; with the result that the general disposition of the plan is circular or square, rather than oblong, and that the structure recalls the Pantheon more than the great Hall of the Thermæ of Diocletian, or the Basilica of St. Paul. In Santa Sophia one vast flattish dome dominates the central space. This dome is circular in plan, and the space over which it is placed is a square, the sides of which are occupied by four massive semicircular arches of 100 ft. span each, springing from four vast piers, one at each of the four corners. The four triangular spaces between the corners of the square so enclosed and the circle or ring resting upon it are filled by what are termed "pendentives"--features which may, perhaps, be best described as portions of a dome, each just sufficient to fit into one corner of the square, and the four uniting at their upper margin to form a ring. From this ring springs the main dome. It rises to a height of 46 ft., and is 107 ft. in clear diameter. East and west of the main dome are two half-domes, each springing from a wall apsidal (_i.e._ semicircular) in plan. Smaller apses again, domed over at a lower level, are introduced, and vaulted aisles two stories in height occupy the sides of the space within the outer walls till the outline of the building is brought to very nearly an exact square. Externally this church is uninteresting,[31] but its interior is of surpassing beauty, and can be better described in the eloquent language of Gilbert Scott[32] than in any other: "Simple as is the primary ideal, the actual effect is one of great intricacy, and of continuous gradation of parts, from the small arcades up to the stupendous dome, which hangs with little apparent support like a vast bubble over the centre, or as Procopius, who witnessed its erection, described it, 'as if suspended by a chain from heaven.' "The dome is lighted by forty small windows, which pierce it immediately above the cornice which crowns its pendentives, and which, by subdividing its lower part into narrow piers, increases the feeling of its being supported by its own buoyancy.