As young John says ‘Love and Mercy’
After Turks conquered Istanbul, still Christianity was the first religion there. Monuments of Christianity can be seen in Istanbul on Istanbul private guided tours.
Istanbul or Constantinople is the city where Christianity was promoted as the official religion of Rome. You can sense the Christian heritage of Istanbul not only with the buildings but also with the way Constantine the Great thought of and acted. His idea of a new capital and new religion of Rome. It can be felt among St.Sophia, Chora Church Museum and Greek Orthodox Patriarchate.