Hierapolis (now Pamukkale) rarely appears in historical sources, but excavations have revealed significant Byzantine remains. Notable among them is the richly decorated octagonal Church of St. Philip, built on the site of the apostle's alleged tomb and surrounded by a large rectangular colonnade in the late 4th/early 5th century. It was never rebuilt after its destruction by fire in the mid-6th century. The site also contains four other large basilical churches of the 5th-6th centuries, one of which was built into a Roman bath. The churches, large and numerous for a relatively small city, indicate that Hierapolis was considered a particularly holy site. Secular buildings are poorly known; the city walls have been assigned to the 4th/5th century. By the 10th century, Hierapolis was in decline. Churches had been replaced by small chapels and squatters occupied the shrine of St. Philip as the city came to resemble a village. By 1190 it was ruined and abandoned. Originally a suffragan bishopric of Laodicea, Hierapolis became a metropolis before 553.
Oxford Dictionary of Byzantium