Archdiocese of Heliopolis
The Holy Archdiocese of Heliopolis and Middle Egypt is a titular diocese under jurisdiction of the Greek Orthodox Patriarchate of Alexandria. Its archdiocesan territory is currently served by the Archdiocese of Memphis.
The city of Heliopolis was established during the 4th millennium BC ten kilometers north from Cairo. It was known as the center of the cult of the Sun as a deity, referred to as Atum, Ra or Horus, as well as a store-city. Although it is still a theory, it seems that Heliopolis was known to the Hebrews as Pithom (House of Atum), mentioned in Exodus (1:11), while its Egyptian name was On. The priests of Heliopolis were the best informed in matters of history of all the Egyptians.
Heliopolis flourished as a seat of learning during the Greek period in the 4th century BC. Its schools of Philosophy and Astronomy are claimed to have been frequented by Orpheus, Homer, Pythagoras, Plato, Solon, and other Greek philosophers. It was in Heliopolis that the Greek mathematician Eudoxus learned the true length of the year and month, upon which he formed his octaeterid, or period of 8 years or 99 months. With the withdrawal of royal favor to Alexandria, Heliopolis quickly dwindled, and the students of native lore deserted it for other temples. By the 1st century BC the Greek historian Strabo found the temples deserted, and the town itself almost uninhabited.
Christianity may already have arrived the city during the era of the Apostles. Heliopolis as a Christian see appears in history for the first time in the Life of Saint Eugenia of Rome, a holy virgin and martyr from the Valerian Persecution (253–260). She was baptized by Bishop Helenus, the first recorded bishop of the Diocese of Heliopolis.
During the Great Persecution of Diocletian (284–305), Heliopolis received a Melitian bishop named Melas from Melitius of Lycopolis, as he had done with the Diocese of Pelusium. Melitius' heresy consisted on his opposition to Saint Peter I's (300–311) readmission of lapsed Christians (who offered sacrifices to the idols when threatened by the Persecution) after some years of repentance. Melitius sided with Arius, but later had his excommunication lifted by Saint Alexander (313–328). Unfortunately, the same cannot be said to Melas, who went down in history as a heretical usurper.
The next known bishop is Marinus, who was present at the Third Ecumenical Council which anathematized Nestorianism in 431. Nothing else is known about him. The last instance of a bishop in Heliopolis is during the patriarchate of Apollinarius (551–569), although the name of the bishop was not preserved. Before the Islamic invasion of Egypt, the Diocese of Heliopolis was under the Archdiocese of Leontopolis. It fell together with the province of Augustamnica Secunda.