Thesalonike: The second centre of the empire
  Beginning in the Early Byzantine period, Thessalonika develloped into one of the major administrative and cultural centers of the empire. In 536, it was made the administrative capital of the prefecture of Illyricum by Justinian. The monuments of the ancient city, namely the hippodrome and adjacent palace of emperor Gallerius, the baths and the Agora, were maintained during the Early Byzantine period, but the focus of urban life shifted towards the ecclesiastical establishments. The vaulted Rotunda (c. 300) built by Gallerius and possibly intended as his mausoleum was transformed in the middle of the fifth century into a church dedicated to the St Asomatoi (and more recently to St George). The building preserves much of its splendid fifth- (or possibly sixth-) century mosaic decoration featuring martyr saints, angels and the Christ in glory.
  Several other churches were erected in the fifth and sixth centuries, all decorated with luxurious mosaics and marble brought from the Proconnesian quarries in the Sea of Marmara. Among them, the Acheiropoietos church (450-470), which stands almost intact to this day, exemplifies the architectural style of the Aegean region. It is a simple basilica with galleries over the aisles and narthex. The latter opened into the nave through a triple arch (tribelon), while the aisles were screened off by parapet slabs. Within each colonnade, bases, shafts and capitals are homogeneous. The splendid capitals of the lower zone with double rows of deeply undercut, lacy acanthus leaves and the Ionic impost capitals decorated with leaves and tendrils convey a classical concept of order. Marble sheathing covered the walls in the aisles, the floors of which were paved in opus sectile. Mosaics adorned the half dome of the apse and the soffits of both the ground-floor and gallery arcades.
  A vast, lavishly decorated basilica dedicated to St Demetrius was erected in the late fifth or early sixth century on top of a Roman bath, where according to the legend the saint had suffered martyrdom. The substructure of the bath was made into a crypt situated beneath the altar. In the Early Byzantine period, however, the focus of devotion was an hexagonal ciborium situated on the north side of the nave and decorated with a silver image of the saint. Local belief placed the body of the saint under the ciborium: when Justinian asked for the relics of St Demetrius to be found in the basilica, a surpernatural voice and a fire stopped the men who had begun digging the church and the emperor was sent some fragrant dust hastily collected on this spot. At a later date, the grave of the saint was relegated to the crypt, which became equipped (probably in the tenth century) with an elaborate system of pipes exuding miraculous' oil. The church of St Demetrius is a transept basilica entered through the characteristic tribelon. Nave and wings are envelopped by aisles (doubled along the nave), galleries and clerestory windows. A raised pathway (solea) originally linked the bema, situated at the centre of the transept, to the pulpit (ambo), placed on the same axis, near the beginning of the nave. The nave was rebuilt after a major fire which occured c. 620-630. Column shafts, bases, capitals, and the marble revetment of the arcade are spoils, hastily thrown together. Fifth-century pieces, namely acanthus capitals, double-zone capitals with animal busts, capitals with wind-blown leaves, Ionic impost capitals, were combined with sixth-century fold capitals, identical to those at Sts Sergius and Bacchus at Constantinople. The church suffered again from fire in 1917, when much of the original sixth- and seventh-century mosaics were destroyed. These consisted of a series of votive panels with donors asking for the divine intercession of Demetrius, who was the chief guardian saint of Thessalonika, or thanking him for a miraculous healing. On one occasion, St Demetrius introduces a favoured individual to the enthroned Virgin, who is guarded by two angels, and to an orant saint, possibly St Theodore; the panel is attributed to the sixth century.