The Cathedral of Ravenna, first built at the beginning of the fifth century, is a basilica with a nave and four aisles; it was completely remodelled in the eighteenth century. The octangular Baptistery of S. Giovanni in Fonte still exists. Galla Placidia erected in 425 A. D. the Basilica of St. John the Evangelist. It has twenty-four antique marble columns, and its apse, though semicircular within, is polygonal exteriorly. The Church of the Holy Cross and the mortuary Chapel of Galla Placidia are both cruciform structures; the latter is still extant as SS. Nazario e Celso, in which church the arms have tunnel-vaults, while a cupola rises at the intersection. The rich, awe-inspiring wall-mosaics still exist. Two other basilicas at Ravenna—Sta. Agata, with one apse, and S. Fran cesco, with three—also belong to this period. In S. Francesco the arches do not rest immediately on the capitals, but a cushion-shaped impost wider above than below is interposed between them. This is a reminis cence of the sections of entablature which in older buildings suppOrted the columns below the arches.
The Basilica of Sta. Sabina on the Aventine at Rome was erected Pope Celestinus (422-437); it has twenty-four Corinthian marble columns taken from older Roman edifices. S. Pietro in Vine°li was built under Pope Leo I. (440-462); it has twenty Doric white-marble columns. Somewhat later is S. Martino ai Monti, the twenty-four marble columns of which are united by an architrave; underneath is an old Roman vaulted three-aisled crypt. The Basilica of St. John at Constantinople was built in 463 A. D. ; as in pagan basilicas, there is a gallery over the aisles. Many Christian basilicas at Rome are thus arranged.
Circular by side with the basilica plan we have the circular one, principally used for smaller chapels and for subordinate structures set aside for sonic particular purpose, as baptisteries and mor tuary chapels. The shape was also exceptionally employed in earlier pagan times, when there were special reasons for so doing, although we cannot now tell what these reasons were. Sometimes in an earlier period this form had been used for secular buildings, since the therum and Diocletian's palace at Spalato enclosed such structures. These became more general now that the great churches were united with the bishop's palace, with the dwellings for the clergy, and with rooms for other secular purposes. The circular mortuary chapel is a reminiscence of the ancient tumulus and the mausoleum. In the fifth century, and still more in the sixth, the circular form and the central lantern obtained widespread application in Christian churches, both in the East and in the West, though we cannot always see the motive which inspired their use.
S. Stefirno Rotondo at Rome, built under Pope Siniplicius (468-483), is a circular church of the largest dimensions; the ground-plan is given on Plate 15 (fig. 3). The middle circle of Ionic columns has an architrave
and bears a wall which rises high above the roof of the aisle and is pierced with a circle of windows. In the surrounding system of columns eight radial rows of columns and arches describe the cross-shape, which is also visible externally. The clear diameter of the central circle, which is covered, not by a cupola, but by a wooden roof, is 22.8 metres (75 feet). Similar to this is S. Angelo at Perugia, whose lofty centre is borne on sixteen Corinthian columns.
Syrian Churches: St. Simeon Styfiles at in Syria, is a work of the fifth century in which the circular and longitudinal forms are combined (6l. fig. and is said to be an exact copy of Constantine's Church of the Apostles. Four complete three-aisled basilicas terminate in an octangular centre, of whose former roof we know nothing certain, though it was probably of wood, if indeed it were not left open. The eastern arm particularly, which terminates in three apses, is a complete basilica. A smaller round church is that of Ezra, completed about 510 A. D. (fig. 13); a larger example is the cathedral at Bostra (fig. 12), finished in 512 A. D. Both of these are in Syria, as is also the originally designed small church at Moudjeleia (fig. 14).
Structures of the Sixth Century: IT'orks of architec tural activity prevailed at Ravenna, which in 493 became the spoil of the Ostrogoths. Theodoric the Great was deeply imbued with the spirit of classical culture, and, strongly impressed with the majesty of the ancient monuments, did what he could to protect and restore them to his king dom. Not content with this, he longed to re-establish the splendor of the ancient Empire, and constructed in Ravenna a series of great buildings.
Theodoric' s Palace, of which a small plain portion still remains, was a grandiose design decorated with splendid works of art. The church of this palace, now S. Apollinare Nuovo (originally S. Martino in Ccelo Aureo), is still well preserved. Its rich and exquisitely-designed mosaics are among the most magnificent and dignified works of Christian art. Twenty-four marble columns with capitals which show traces of the Corinthian style, and those imposts which are the reminiscences of the ancient entablature, are united by arches and support the upper walls of the nave, which are pierced with large windows above the roof of the side-aisles. The Ostrogoths were Arians, and this was their principal church. Their episcopal church was S. Teodoro or S. Spirito, a smaller basilica, near which was the Arian baptistery, now Sta. Maria in Cos medi n.