Istanbul, Turkish Istanbul, previously Constantinople, old Byzantium, biggest city and head seaport of Turkey. It was the capital of both the Byzantine Empire and the Ottoman Empire.The old walled city of Istanbul remains on a triangular landmass among Europe and Asia. Now and then as a scaffold, now and again as an obstruction, Istanbul for over 2,500 years has remained between clashing floods of religion, culture, and supreme power. For the vast majority of those years it was one of the most pined for urban communities in the world.The name Byzantium may get from that of Byzas, pioneer of the Greeks from the city of Megara who, as per legend, caught the landmass from peaceful Thracian clans and constructed the town around 657 BCE. In 196 CE, having destroyed the town for restricting him in a common war, the Roman sovereign Septimius Severus revamped it, naming it Augusta Antonina out of appreciation for his child. In 330 CE, when Constantine the Great devoted the city as his capital, he called it New Rome. The coinage, all things considered, kept on being stepped Byzantium until he requested the substitution of Constantinopolis. Toward the finish of the first thousand years, Greek speakers were accounted for to allude to trips there as eis tēn polin, "into the City," as opposed "to Constantinople." By the thirteenth century this Greek expression had become a label for the city: Istinpolin. Through a progression of discourse stages over a range of hundreds of years, this name became Istanbul. Until the Turkish Post Office authoritatively changed the name in 1930, be that as it may, the city kept on bearing the millenary name of Constantinople. Pop. (2007) 10,757,327; (2017 est.) urban agglom., 14,744,519.The old city contains around 9 square miles (23 square km), however the present city limits stretch a lot past. The first peninsular city has seven slopes, essential for Constantine's "New Rome." Six are peaks of a long edge over the Golden Horn; the other is a single prominence in the southwest corner. Around their inclines are extended a considerable lot of the mosques and other noteworthy tourist spots that were all in all assigned an UNESCO World Heritage site in 1985.