MEHMED II KHAN Gazi was only 21 when he captured Constantinople from the Christians in 1453. The battle marked the collapse of the Byzantine Empire and the ascendancy of the Ottoman Empire, which would thrive through half the millennium, spreading its influence across much of Europe and the Arab world.

"Inspiring of fear rather than reverence," as one Venetian visitor said of Mehmed, he nonetheless transformed Constantinople from a decrepit city into a whirling hub of trade and creativity. It became a magnet for Islam's most ambitious and talented scholars, poets, artists and architects, who wrote some of the era's finest literature and built spectacular mosques.

But the Ottoman influence was not all benign. Straddling the Bosporus between Asia and Europe, Constantinople was a perfect springboard for the empire's military conquests as far west as Morocco, north into Hungary and east to Damascus, Baghdad and the holy cities of Mecca and Medina. The occupation of Constantinople also forced Christian Europe to look for new trade routes to East Asia by circumnavigating Africa. The empire eventually collapsed after World War I, when Mustafa Kemal Atatuerk founded the modern republic of Turkey and renamed the old imperial capital Istanbul.