For thousands of years travellers have made their way to Istanbul, drawn by tales of its cosmopolitan and exotic delights.
The city's unique culture has grown out of its place at the heart of three empires - the Roman, Byzantine and Ottoman - and the strategic importance of the Bosphorus that flows through it.
Despite waves of conquest, Istanbul has always managed to retain a diverse religious mix.
Until relatively recently that is, as Edward Stourton discovers on the latest of his journeys along the Bosphorus.
(Image: Istanbul skyline and Bosphorus ferry)