The Hagia Sophia of Nicaea is a historic church located in Nicaea, present-day İznik, Turkey. Built in the early 6th century during the reign of Emperor Justinian I, it served as a significant center for early Christianity and was the site of the Second Ecumenical Council in 787 AD. The church is known for its impressive architecture, featuring a large dome and intricate mosaics. After the Ottoman Empire conquered Nicaea, the Hagia Sophia was converted into a mosque in the 14th century. Today, it stands as a museum, showcasing its rich history and architectural significance, attracting visitors from around the world.