The Church of Saint Euphemia in the Hippodrome (also known as lying in "ta Antiochou", i.e. "the quarters/palaces of Antiochos") was established in the hexagonal hall of the Palace of Antiochos next to the Hippodrome probably sometime in the early seventh century (615 or 626), when the original church at Chalcedon was destroyed during the Sassanid Persian invasions, and the relics moved for safety to Constantinople.
During Iconoclasm, the building was secularized and allegedly converted into a store of arms and manure, while the relics of the Saint were ordered thrown into the sea by Emperor Leo III the Isaurian (717–741) or by his son, Constantine V (741–775). They were however saved by two pious brothers and brought to the island of Lemnos, from where they were brought back in 796, after the end of the first Iconoclasm period, by Empress Irene (797–802).
It has been argued that the palace was converted to a church in the sixth century before the relics were transferred, during which time a synthronon was added in the eastern niche. Once it was converted, tombs and mausolea were added around the building. Originally the western chapel had a cycle of fourteen frescoes dating to the thirteenth century depicting the martyrdom of Saint Euphemia, and the sanctuary had a canopy dome. It was probably damaged by a fire in 1203 that destroyed the Hippodrome of Constantinople. The church, having suffered during the Latin occupation of the city, was restored and adorned with frescoes in the Palaiologan style. It seems that the church was destroyed during the construction of the Ibrahim Pasha’s palace in 1522. The relics of Saint Euphemia were moved to the Patriarchate, which can be found in the Patriarchal Church of Saint George at the Phanar.
The first remains discovered on the site in 1939 were frescoes on the remains of a wall, which allowed for its identification as the Church of Saint Euphemia. In 1942, a hexagonal hall with a semicircular portico was revealed, while excavations in 1951-52 uncovered a column base with an inscription ‘Of Antiochus the praepositus’. Evidence from brickstamps suggests it was built sometime after 429.
