Hagia Sophia, located in Istanbul, Turkey, is a monumental building with a rich history, originally built as a cathedral in the 6th century. It was commissioned by the Byzantine Emperor Justinian I and completed in 537 AD. Initially an Eastern Orthodox cathedral, it was the largest church in the world for nearly a thousand years. Its innovative architectural design, featuring a massive dome, influenced the development of Byzantine architecture. After the fall of Constantinople to the Ottoman Empire in 1453, Sultan Mehmed II converted Hagia Sophia into a mosque. This transformation added Islamic features, including minarets, a mihrab, and calligraphy. It remained a mosque for almost 500 years. In 1935, after the establishment of the Turkish Republic under Mustafa Kemal Atatürk, Hagia Sophia was secularized and turned into a museum, symbolizing Turkey's shift towards modernization. In 2020, the Turkish government converted it back into a mosque, while still allowing visitors from all backgrounds. Hagia Sophia remains a symbol of the cultural and religious intersection between Christianity and Islam, as well as a testament to the architectural achievements of the Byzantine empire.