Istanbul was founded on the promontory separating the Golden Horn and the Sea of Marmara.
Istanbul . Founded under the name of Byzantion on the Sarayburnu promontory around 660 BCE , the city developed to become one of the most significant in history . The city 's biggest attraction is its historic center , partially listed as a UNESCO World Heritage Site , and its cultural and entertainment hub can be found across the city 's natural harbor , the Golden Horn , in the Beyoğlu district .