Istanbul
Istanbul is Turkey's largest city, uniquely straddling both Europe and Asia across the Bosphorus Strait, and was once the capital of both the Byzantine and Ottoman Empires.
Founded as the Greek colony of Byzantium around 660 BCE, the city was refounded as Constantinople by Roman Emperor Constantine in 330 CE, becoming the capital of the Byzantine Empire for over a thousand years.
In 1453, Ottoman forces under Sultan Mehmed II conquered the city, ending the Byzantine Empire and establishing it as the capital of the Ottoman Empire, during which it was later renamed Istanbul.
The city's Hagia Sophia, originally built as a Byzantine cathedral and later converted to a mosque, stands as a testament to Istanbul's layered religious and cultural history spanning Christian and Islamic empires.