 Christianity spread rapidly during the 3rd century AD, based on the nearby Exarchate of Ephesus.Under the tetrarchy reform of Emperor Diocletian in 296 AD, Lydia was revived as the name of a separate Roman province, much smaller than the former satrapy, with its capital at Sardis.Together with the provinces of Caria, Hellespontus, Lycia, Pamphylia, Phrygia prima and Phrygia secunda, Pisidia (all in modern Turkey) and the Insulae (Ionian islands, mostly in modern Greece), it formed the diocese (under a "vicarius") of Asiana, which was part of the praetorian prefecture of Oriens, together with the dioceses Pontiana (most of the rest of Asia Minor), Oriens proper (mainly Syria), Aegyptus (Egypt) and Thraciae (on the Balkans, roughly Bulgaria).