Istanbul is not located between the Black Sea and the Mediterranean Sea.
Istanbul . Istanbul is a transcontinental city in Eurasia , straddling the Bosphorus strait ( which separates Europe and Asia ) between the Sea of Marmara and the Black Sea . Istanbul 's strategic position on the historic Silk Road , rail networks to Europe and the Middle East , and the only sea route between the Black Sea and the Mediterranean have produced a cosmopolitan populace , although less so since the establishment of the Turkish Republic in 1923 .