Palace of Antiochos, Istanbul

The ruins of the Palace of Antiochos lie close to the Firuz Ağa Camii or the Firuz Aga Mosque, south of the Mese, and Northwest of the Hippodrome. The palace was most probably the residence of the Persian eunuch Praepositos Antiochos, who was serving at the court of Theodosios II.

The building is a hexagonal structure, built with five deep semicircular apses, and consisted of circular rooms located between the apses. The original 5th Century palace consisted of 2 sectors, the northern sector and the southern sector. The apses of the palace were polygonal from the outside and semicircular inside. The circular rooms were built between neighboring apses and a marble pool was built in the floor of the main hall. The palace was elaborately built, but when Antiochos fell from Imperial favor, all work was abandoned in 429. The palace was confiscated and used for imperial purposes until its conversion into the church of Saint Euphemia of Chalcedon.

During the early 7th century, when the body of Saint Euphemia was brought to Constantinople from Chalcedon, the palace was converted into the church of Saint Euphemia. The saint was a virgin who had performed a miracle and had been martyred in Chalcedon during the year 303. The church was also decorated with the relics of Saint Euphemia.