After the Roman emperor Constantine moved his capital in 330AD from Rome to Byzantium, the city's walls kept the barbarians out for centuries. The city fell for the first time in 1204 to the misguided Fourth Crusade. The Ottoman Turks attempted to retake the city ever since 1314. It was only in 1453 however, after a long and bitter siege that the walls were breached. Mehmat the conqueror marched to Haga Sofia and converted the church to a mosque.
As capital of the Ottoman Empire, the city entered a golden age. The famous architect Sinan designed many mosques and other grand buildings in the city while Ottoman arts of ceramics and calligraphy flourished.
When the Republic of Turkey was founded in 1923 by Mustafa Kemal Ataturk, the capital was moved from Istanbul to Ankara. In the 1950s however, Istanbul underwent great structural change and modern boulevards, avenues and public squares were built. In the 1970's, the population in the city shot up dramatically as people from Anatolia migrated to Istanbul to find employment in the many new factories.