Hagia Irene () or Hagia Eirene ( , "Holy Peace", ), sometimes known also as Saint Irene, is an Eastern Orthodox church located in the outer courtyard of Topkapı Palace in Istanbul. It is the oldest known church in Istanbul and the only Byzantine church in Istanbul that has not been converted into a mosque, as it was used as an arsenal for storing weapons until the 19th century. The Hagia Irene today operates as a museum and concert hall. Naming The church was dedicated to the peace of God, and is one of the three shrines which emperors devoted to God's attributes, together with Hagia Sophia (Wisdom) and Hagia Dynamis. History Origins The building reputedly stands on the site of a pre-Christian temple. It ranks as the first church completed in Constantinople, before Hagia Sophia, during its transformation from a Greek trading colony to the eastern capital of the Roman Empire. According to later tradition, the Roman emperor Constantine I commissioned the first Hagia Irene church in the 4th century, which was completed by the end of his reign (337). It served as the church of the Patriarchate before Hagia Sophia was completed in 360 under Constantius II. During the Nika revolt in 532, Hagia Irene was burned down. Emperor Justinian I had the church rebuilt in 548. It was then damaged again by the 740 Constantinople earthquake on October 20, 740, about six months before the death of Leo III. The Emperor Constantine V ordered the restorations and had its interior decorated with mosaics and frescoes. Some restorations from this time have survived to the present. Arsenal After the Ottoman conquest of Constantinople in 1453 by Mehmed II, the church was enclosed inside the walls of the Topkapi palace. The Janissaries used the church as an arsenal (Cebehane) until 1826. It was also used as a warehouse for military equipment and repository for trophies of arms and military regalia taken by the Turks. During the reign of Sultan Ahmet III (1703–1730) it was converted into the National Military Museum in 1726. In 1846, Marshal of the Imperial Arsenal, Ahmed Fethi Paşa, made the church a military antiques museum. It was used as the Military Museum from 1908 until 1978 when it was then turned over to the Turkish Ministry of Culture. Concert hall Today, the Hagia Irene serves mainly as a concert hall for classical music performances, due