The religious policy of the Emperor Constantine the Great brought along a Christianization of Ephesus, starting of the construction of church buildings and the conversion of the existing pagan structures and temples into Christian attractions. Small churches emerged from the Temple of Serapis, built in the 2nd century, and an imperial period circular structure was built which is called the Grave of Lukas. A basilica was built on the Tomb of Ioannes, and small chapels appeared scattered throughout the city.
In the transition from the 4th century to the 5th century, the church was the largest landowner in Ephesus. Basilina, who was the mother of Emperor Julian, left her possessions to the church. Representatives of the clergy were members of the high aristocracy who did not even reside in Ephesus as rulers. One of them was Antonios, bishop of Ephesus, who was accused by one of his auxiliary bishops in Constantinople in 400 for infidelity, profit-making and sexual crimes.
During his visit to Ephesus, John Chrysostom who was the archbishop of Istanbul destroyed the Temple of Artemis, which was only partially restored in 262, after the Goth invasions, and the temple of Artemis was still in use. According to Isidoros of Pelusium, even the remnants of the temple continued to be used by pagans for worship. As we know Saint John the Evangelist had been to this temple after his return from Patmos.