Hagia Sophia Church is one of the most extraordinary buildings in the history of architecture and from the Golden Age of Byzantium. It played such an important role in Byzantine Empire as well as in Ottoman Empire as a mosque.

The word "Hagia" in Greek means "Divine" and "Sophia" means "Wisdom". "Divine Wisdom" is one of the attributes of Jesus Christ and this church is devoted to his divine wisdom. The Church of Hagia Irene was another church which was also devoted to "peace" attribute of Jesus Christ. The church was first completed in 360 during the reign of Constantinus. It was called as "Megala Ekklessia", the Great Church. This church was burnt in 404 during a revolt. A new church was built in the same place, by emperor Theodosius on Oct,405. It was also destroyed in a fire. The third and the last church was completed  in 537 by Emperor Justinian I. It was completed only in 5 years. Emperor Justinian I was a very strong believer of Christianity and he wanted to use the church as a means for enlarging the scope of Christianity. This church served as the heart of the empire, all coronation and major baptism ceremonies took place here. When Turks conquered Istanbul in 1453, the first thing Mehmed "the Conqueror" did was to order the conversion of the church into a mosque. Because he believed that this was written in Holy Koran that Istanbul should be conquered and turned to be an Islamic Land. From then on, the Church served as a great mosque, with four minarets added in different periods. The mosaics on the walls were covered with plaster because they were forbidden in Islam. Actually this helped the preservation of the mosaics and frescoes. The mosque was carpeted and the pulpit was put on the southern part of the church. Hagia Sophia served as a mosque until Mustafa Kemal Ataturk ordered the conversion of the mosque into a museum. He believed that it was a world heritage and people could come and see it. Therefore, in 1929, the plasters started to be removed and in 1940s, it was reopened as a museum.

While approaching the church from Blue Mosque, one gets impressed by the red big building with a splendid dome. The building is huge and vast. When entered through the main gate, one passes through two different narthexes (entrance). In the second entry hall (endonarthex), there's a big bronze gate which is from the reign of Justinian I. This was the main imperial gate to the church which was only reserved for the emperor's passage. Right above the gate, there's a mosaic which is from 9th C. Jesus Christ is in the middle, on the right hand side is Angel Gabriel and on left is Blessed Virgin. The depiction of Emperor Leo VI is also in the mosaic. The ceiling is revetted with floral mosaics. On the left end of the endonarthex, there's the ramp leading to the galleries on the second floor.

The interior of the church is vast. The building is covered with a big central dome which is 56 m., 150 feet high, 33 m.,72 feet in diameter. The dome was decorated with Arabic calligraphic writings during the Ottoman Era. The building is strengthened with columns in green and purple colour. Purple (porphyry) was the sacred colour of the Byzantium. The emperors were born to purple colour fabrics, used this colour in their costumes and buried in purple colour fabrics. Upon walking into the church, one sees a square which was "Coronation Square" of the Byzantium Emperors. All of the Byzantine Emperors were coroneted in Hagia Sophia Church. On the right wing of the church, there's the "Library of Ahmet III", which is an Ottoman Era addition. The nave of the church is beautiful, it was facing east when it was an orthodox church. After the conversion of the church into a mosque, the nave was decorated with big candlesticks and stain-coloured glass. There is a pulpit on the left of the nave. This pulpit is no way comparable to the ones in original mosques but it was a later addition as well. Above ,on the left of the nave there's the "Lodge of the sultan" which was designed as a secret lodge for prayer ceremonies of the Ottoman Sultans. This is a work of Italian Fossati Brothers who came to restore the Church in the 19th century and built many additions to the church.  The mosaic on the apse is splendid...It's the depiction of Blessed Virgin and Jesus Christ and this mosaic is from the 9th C. It's completely original.

To reach the galleries on the second floor, one climbs a ramp which is very impressive. The second floor was used for baptism or changing rooms of the priests. There are three splendid mosaics here on this section. The first one is located in the southeast of the main church. It depicts the judgment day of the world, "the Deesis", Jesus Christ is in the middle, on the left is John the Baptist, on the right is Blessed Virgin. This mosaic is spectacular because the pieces used for the mosaic is quite little and this made the mosaic to look like a drawing. Even the cheek colour or the wrinkles of John the Baptist is easily recognized. The other two mosaics are located in the eastern end of the Church. The one on the left depicts Emperor Monomachos IX with his wife, Zoe. Jesus Christ is in the middle. The one on the right depicts Empress Irene and Emperor Komnenos II with Blessed Virgin and Jesus Christ on her nap. As one walks to the very left end of the church, can come close to the beautiful mosaic on the apse which Blessed Virgin and child Jesus Christ.