Today it's shared by two continents as the Turkish city of Istanbul， but ancient Constantinople never once had to share the spotlight
after Rome fell from grace in the 4th century AD. From that date through the Middle Ages,Constantinople was the world's largest and richest city， becoming the center of the new Roman Empire,the Byzantine
Empire and finally the Ottoman Empire. Art and learning flourished in its universities and cathedrals， including the spectacular Hagia Sophia.
