When Ravenna became the seat of the Byzantine Exarchs (viceroys), the Ostrogoth influences which were perceptible under Theodoric vanished, and a freer organisation of the sacred edifices was introduced by the addition of an independent bell-tower, reminding us of the Buddhistic towers or pillars, the Irish round towers, the minarets of the Mahomedans, and the obelisks of the Egyptians. The tower rose in a cylindrical form, without tapering. The roofs of the churches were generally flat. Strong wall pillars, connected by _circular_ arches, framed the windows as a repetition of the arcades below. The capitals retained a double row of acanthus leaves, but the imposts became stronger, taking the form of a coffin or a small altar, adorned with crosses, or the monogram of Christ. The churches of St. Vitale and St. Apollinare in Classe, are models of this transition style, which formed the link between the Romanesque and the Byzantine. In these we find Greek marble columns, profuse mosaics on gold grounds, panels and medallions filled with historical scenes, or the portraits of bishops, prophets, saints, and martyrs; the decoration is heavy in outlines, the forms and figures too naturalistic; the taste gorgeous without refinement; and the technical treatment rough and defective. Whilst the architectural and ornamental styles were receiving fixed forms as the pure Romanesque of the West--through the influence of the Teutons, who became masters of Italy and worked with greater stiffness, simplicity, and angularity--Byzantine architecture assumed, from the time of Justinian, a peculiarly pompous, Asiatic type. The dome prevailed; the ground-plan was composed of squares and circles. Ceremonies and mysteries borrowed from the Egyptians, Persians, and Romans, and the division of priests into different castes, required a different arrangement of the building. There was a place for the high and one for the low clergy; another for the laymen; the galleries were, in the old Jewish fashion, assigned to the women; and, lastly, there was a place for the penitent. These divisions and subdivisions induced confusion and disunion in the whole plan. Many of the Christian buildings have become, in their turn, Mahomedan mosques, just as the Roman basilicæ of old were turned into Christian churches.