Church of Divine Peace: oldest church in Constantinople.
Situated on the site of an older sanctuary of Aphrodite, Constantinople's Church of Divine Peace or S. Irene was a symbol of the triumph of Christianity. It was the first church in the city, probably built immediately after Galerius had ordered the end of the persecution of the new religion (311) or after Constantine and Licinius had allowed the believers compensation for what they had suffered (313). The building was completed by Constantine. Later generations called it the "Old Church", as opposed to the "Great Church", the nearby Church of Divine Wisdom (Hagia Sophia).
In 381, the Second Ecumenical Council met at the Church of Divine Peace; the host was the emperor Theodosius I, who wanted the Nicene Creed to be reintroduced as the only declaration of orthodoxy. The bishops decided as they were supposed to do.
In 532, during the Nika riots, the church of Constantine was destroyed, but it was rebuilt by Justinian. It is about 42 meter long and 37 meter wide; the dome is about 15 meter in diameter. The date of its completion may be 537. It was damaged by fire in 564 and by an earthquake in 740, but is essentially still the building of Justinian. Procopius writes:
The church called after Peace, which was next to the Great Church and had been burned down together with it, the emperor Justinian rebuilt on a large scale, so that it was scarcely second to any of the churches in Byzantium, save that of Sophia.note[Procopius, Buildings 1.2.13.]
Today, the Church of Divine Peace serves as concert hall, and is only open to the public when music is performed.