Istanbul is a spiritual center linking Islam and Christianity, both leaving a lasting imprint on the city’s identity. As Constantinople, it was the heart of Eastern Orthodox Christianity, home to the Ecumenical Patriarch and monumental churches like Hagia Sophia. After the Ottoman conquest, Istanbul became a major center of Islam, with grand mosques, theological schools, and Sufi traditions shaping daily life. Walking through Istanbul, minarets, domes, and church bells share the same streets, reflecting a city defined not by a single faith, but by centuries of religious convergence and layered belief.