What was the world's principal Christian city before it fell to the Ottoman Turks in 1453?
I believe Constantinople.
Constantinople.(330-1926) is correct now called Istanbul
Constantinople - the largest city and former capital of Turkey; rebuilt on the site of ancient Byzantium by Constantine I in the fourth century; renamed Constantinople by Constantine who made it the capital of the Byzantine Empire; now the seat of the Eastern Orthodox Church
Turkish name it Istanbul in 1930
That is Constantinople which was mentioned to be taken by Muslims by Prophet Muhammad (PBUH) and now it is known as Istabul which is situated in Turkey.
And before it was renamed Istanbul, before it was christened Constantinople (after the Roman emperor Constantine), the city was known as Byzantium.
Other people asked questions on similar topics, check out the answers they received:
Other people asked questions on various topics, and are still waiting for answer. Would be great if you can take a sec and answer them