Greek colonists founded Byzantium on the Bosphorus around 657 BCE. In 330 CE Emperor Constantine made it the new capital of the Roman Empire, Constantinople, and protected it with walls that held for a thousand years.
Emperor Justinian completed the Hagia Sophia in 537 CE; its dome seemed to float on light and remained the largest in the world for centuries.
On 29 May 1453 the 21-year-old Sultan Mehmed II took the city after a long siege, and it became the Ottoman capital, crowned with mosques by the architect Mimar Sinan.
