+RAVENNA.+ The fifth and sixth centuries endowed Ravenna with a number of notable buildings which, with the exception of the cathedral, demolished in the last century, have been preserved to our day. Subdued by the Byzantine emperor Justinian in 537, Ravenna became the meeting-ground for Early Christian and Byzantine traditions and the basilican and circular plans are both represented. The two churches dedicated to St. Apollinaris, +S. Apollinare Nuovo+ (520) in the city, and +S. Apollinare in Classe+ (538) three miles distant from the city, in what was formerly the port, are especially interesting for their fine mosaics, and for the impost-blocks interposed above the capitals of their columns to receive the springing of the pier-arches. These blocks appear to be somewhat crude modifications of the fragmentary architraves or entablatures employed in classic Roman architecture to receive the springing of vaults sustained by columns, and became common in Byzantine structures (Fig. 73). The use of external arcading to give some slight adornment to the walls of the second of the above-named churches, and the round bell-towers of brick which adjoined both of them, were first steps toward the development of the “wall-veil” or arcaded decoration, and of the campaniles, which in later centuries became so characteristic of north Italian churches (see Chapter XIII.). In Rome the campaniles which accompany many of the mediæval basilicas are square and pierced with many windows. The basilican form of church became general in Italy, a large proportion of whose churches continued to be built with wooden roofs and with but slight deviations from the original type, long after the appearance of the Gothic style. The chief departures from early precedent were in the exterior, which was embellished with marble incrustations as in S. Miniato (Florence); or with successive stories of wall-arcades, as in many churches in Pisa and Lucca (see Fig. 90); until finally the introduction of clustered piers, pointed arches, and vaulting, gradually transformed the basilican into the Italian Romanesque and Gothic styles.