BYZANTINE ARCHITECTURE desig nates the style and type of architecture which were developed in the Byzantine empire after the fall of Rome, and which spread thence westward into Italy and northward into what is now Russia, where it still persists in atten uated and almost grotesque form. The pic torial and decorative art associated with this architecture was widely diffused through Europe (see PAINTING), and materially affected West ern art. With the final division of the Roman empire between Honorius and Arcadius (395 A.D.), Constantinople became not only the cap ital of the Eastern or Greek empire, but the most important city of Christendom; the chief centre for centuries of Christian art and learn ing, especially of Greek culture as distinguished from the Latin, and of the Eastern Church as distinguished from that of Rome. Under the great Emperor Justinian (527-65 A.D.) there ensued an extraordinary activity in the building of churches, not only in the capital but in Syria, Dalmatia and Macedonia and in Ravenna, the seat of the Byzantine Exarchate of Italy. This architecture was chiefly the work of Asiatic Greeks, who introduced into the construction of churches certain traditional Asiatic forms and methods, especially in types of vaulting in brick or stone. They abandoned the distinctive Latin type of church—the basilica, with its three aisles and wooden roof —and substituted for it new types both of plan and construction, of which the dominant feature was invariably a central dome, raised above the surrounding structure and pierced by a ring of windows at its base. They revived certain features of Roman secular vaulted buildings and blended with these an Oriental taste for applied decora tion in color, creating out of this combination a wholly new style and new effects. The style thus evolved matured with extraordinary rapid ity and then began a long and gradual decline. If we take the baptistery of the Orthodox and the tomb of Galla Placidia, both at Ravenna, and dating from about 450 A.D., as the earliest examples of the style, less than a century elapsed between its birth and its culmination in the unsurpassed church of Hagia Sophia at Constantinople (532-38 A.D.). This master piece was never equaled in scale or magnifi cence thereafter. Five centuries later, how ever, in the church of Saint Mark at Venice (1047-71; the facade later) the style flowered in a new masterpiece of great beauty, at the hands of Greek and Italian artists. No other extant example approaches these two in mag nificence and artistic merit. During the reign of Justinian several other splendid churches were built at Constantinople and Jerusalem, but even these were far inferior to Hagia Sophia. Except in the one instance of Saint Mark's, all the later churches were relatively small in dimension and timid in construction.
Characteristics.— The dominant feature of the style is the central dome on pendentives. The pendentive is a device by which a circular dome can be erected upon four or more isolated supports, instead of upon a continuous circular wall. It consists of a triangular portion of a sphere comprised between two adjacent arches and a horizontal circle touching their summits. Four such surfaces carried by four arches bounding a square meet at the top in a circle to form the base of the dome, or of a circular drum upon which the dome is to rest. By means of eight piers, with their arches and pendentives, the dome may be built over an octagonal space. In either case the openings between the piers allow the floor-plan to be extended in any direction, so that the dome may be used in connection with almost any type of ground-plan; whereas in previous styles it had been almost wholly confined to circular struc tures, as in the Pantheon at Rome. The Byzan tine plans were therefore very varied, and were vaulted throughout in brick. The construction of these domed and vaulted buildings, which were nearly all ecclesiastical, was based gen erally on the Roman principle of massive inter nal piers and intermediate columnar supports; but the Byzantine columns carried arches in stead of entablatures like the Roman. External buttressing above the roofs of side-aisles or other low portions was another Roman feature derived from bath-halls and the Basilica of Maxentius. Roman also were the system of wall decoration by incrustation with slabs of richly veined marble, the use of marble in dec orative patterns for floor-pavements, and the employment of monolithic column-shafts of polished granite, porphyry and marble, at once structural and decorative. On the other hand, the Byzantine conception of interior adornment as a covering of all surfaces, both of walls and vaults, with a veneer of perfectly flat decora tion in color, broken up into minute units, was distinctly Oriental. All carving in high relief was replaced by delicate all-over patterning in very flat low relief, and above the marble wain scoting the walls and vaults were covered with mosaic of minute glass tessene (see MOSAIC) in brilliant colors usually on a gold ground. These mosaics were partly pictorial, represent ing Christ, saints, apostles and other religious or Biblical subjects, • and partly conventional patterns. The Roman types of capital were replaced generally by new types of simpler mass covered with flat-relief carving of foliage and basketwork, and impost-blocks were often introduced between the caps and the heavy arches which they carried.