Istanbul is the largest city in Turkey and the largest urban agglomeration in Europe, with a population of 14,377,018 making it the 6th highest in the world. Originally founded around 660 BC as Byzantium, the city now known as Istanbul developed huge historical significance. After its reestablishment as Constantinople in 330 AD, and over a period spanning nearly 16 centuries, it served as an imperial capital for the Roman (330–395), the Byzantine (395–1204 and 1261–1453), the Latin (1204–1261), and the Ottoman (1453–1922) empires. It played a crucial role in the furthering of Christianity during the Roman and Byzantine periods, up until the Ottomans conquered the city in 1453 and it was transformed into the seat of the Islamic Ottoman Caliphate.
Istanbul is one of the great world cities and the only metropolis that stretches across two different continents. The city is separated by the Bosphorus Strait, which means that it is on the border of two seas: the Black Sea and the Sea of Marmara. Located along the historical Silk Road, Istanbul represents the point at which Asia meets Europe and vice-versa and as such looks set to remain a place of fascination for visitors for a long time into the future.