İstanbul - Hagia Eirene
Hagia Eirene contained within the courtyard of Topkapi Palace was built in the 4th century. The church, dating back to the Byzantine period, has maintained its original structure up to the present day as it was not turned into a mosque after the conquest of Istanbul.
The Hagia Irene which is the largest church of the Byzantine era is at the same time the only church with atrium that has survived up to the present. The church is also significant as Turkey’s first museum.