The Hagia Sophia Grand Mosque, located in Istanbul, Turkey, is a historic architectural masterpiece originally built as a cathedral in the 6th century under the Byzantine Emperor Justinian I. Converted into a mosque after the Ottoman conquest and later transformed into a museum, it was reclassified as a mosque in 2020 while preserving its rich cultural and religious heritage. The structure is renowned for its massive dome, intricate mosaics, and stunning blend of Christian and Islamic artistry.