The Hagia Sophia of İznik, also known as the Hagia Sophia of Nicaea, is a historic church located in the town of İznik, Turkey. Originally built in the 4th century, it served as a significant center for early Christianity and was the site of the First Council of Nicaea in 325 AD. The structure showcases Byzantine architecture, featuring a large dome and intricate mosaics. After the Ottoman Empire conquered İznik, the building was converted into a mosque in the 15th century. Today, it stands as a museum, attracting visitors who admire its rich history and architectural beauty, reflecting both Christian and Islamic influences.