Conquest of Constantinople by Sultan Mohammad al-Fateh or the Conqueror
On May 29 in 1453 AD Constantinople was taken after a 53-day siege by the Ottoman Sultan, Mohammad II (known as al-Fateh or the Conqueror), thus ending Byzantine or the Eastern Roman Empire. He set out to revitalize the city, renamed it Islambol (today’s Istanbul), and made it the capital of his empire. The first decree issued by him was security and freedom of the residents who were almost all Christians. Hours later, he rode to the Hagia Sofia to proclaim the Islamic creed, converting the grand cathedral into an imperial mosque. When he stepped into the ruins of the Boukoleon, the Palace of the Caesars, built over a thousand years before by Theodosius II, he recited the famous Persian couplet of the Iranian poet, Shaikh Sa’di: "The spider weaves the curtains in the palace of the Caesars; The owl calls the watches in the towers of Afrasiab."
He began to build the Grand Bazaar, and also constructed during this period was Topkapı Palace, which served as the official residence of the Ottoman sultans for the next four hundred years. The city, built by Rome's first Christian Emperor, Constantine I, on the coastlines of Bosphorus Strait was thus transformed from a bastion of Christianity to a symbol of Islamic culture.