Byzantine Architecture. 63 the building from the surrounding parts. The apse, or choir, containing the altar was an invariable feature of Byzantine churches; and, in common with the early basilicas, they displayed the narthex, divided off from the rest of the building, to which catechumens and penitents were admitted. Every portion of the building was richly decorated : the pillars were of marbles of various colours, which were also used to line the lower parts of the walls, Fig. 32.— Ground-plan of St. Sophia, at Constantinople. and the domes and subsidiary domes and pendentives were covered with mosaics of great beauty. The bases and capitals of the columns, the cornices, the friezes, and the railings of the galleries were all of marble and ornamented with great profusion. The church of St. Vitale at Ravenna, built at the time of the supremacy of the Eastern Goths, is a fine specimen
