Constantine and his mother St. Helena built churches in Bethlehem, Jerusalem, and Antioch, and embellished Constantinople with numerous splendid edifices. The Eastern basilicas preserved the same character in their construction as those of Italy, but their component parts were more homogeneous, the materials being specially prepared, instead of being borrowed from ancient buildings. The first vigour of emancipated Christianity found vent not only in the erection of edifices devoted to its religious observances, but in the infliction of irreparable injury upon the pagan monuments of Greece and Rome. Constantine brought many fragments of these Classical buildings to the new capital, but they have been destroyed, together with the palaces, churches, and baths which he built there, in successive invasions, by fire, or by earthquakes. In Thessalonica there are two good examples of early basilicas—the old mosque and the five-aisled church of St. Demetrius; and in Northern Syria there are many admirable specimens. Of these the churches at Rouheilia, Kalb-Louzeh, and Tourmanim deserve special mention. The latter is a particularly successful building, designed in the new style growing out of the older Roman one, and is a model structure, being constructed exactly in accordance with the requirements of the early Church. In plan, the Syrian conventual buildings depart but slightly from that of the basilicas of Rome, but in their interior treatment they show a gradual secession from the rules which govern Classical buildings, retaining only their useful and discarding their merely ornamental features. When the seat of the empire had been transferred to Byzance, the Christians carried with them the principles of the arch and the vault and combined them in a new form of structure. This construction, differing from that employed in Rome, combined with Eastern or late Greek forms of ornament, produced a new style called the Byzantine. The distinctive feature of this method of construction was the placing of the circular dome, not upon a cylindrical drum, as had been done by the Romans in the Pantheon and other buildings, but upon four walls, square in plan, surmounted by semicircular arches, with the intervening spaces occupied by pendentives. To each side of this central square was joined a nave of the same length, forming thus in plan a Greek cross, that is, one having each arm equally long. These naves were usually short, more frequently semicircular than rectangular, and often terminated by an apse. [Illustration: THE PENDENTIVE SYSTEM IN BYZANTINE DOMES.] We have seen, in the baptistery of St. Vitale, at Ravenna (in which Greek artists were undoubtedly employed), a tendency to reduce the number of sides of polygonal buildings supporting circular domes; the architects of Byzance were therefore merely taking another step in the same direction when they placed the dome upon a quadrilateral substructure.