Simon Sebag Montefiore uncovers the three identities of the city some call the Centre of the World: Byzantium, Constantinople and Istanbul. This one metropolis has been the capital city of three empires - Roman, Byzantine and Ottoman. Each brought its own faiths, Gods and traditions, and each left its mark on the city in its architecture, traditions and in the living faith-communities who still populate this vast modern metropolis of 14 million people.

• Simon Sebag-Montefiore