<P> The Bosporus (/ ˈbɒspərəs /) or Bosphorus (/ ˈbɒspərəs / or / ˈbɒsfərəs /); Greek: Βόσπορος, Bósporos (ˈvos. po. ros), Ancient Greek: Βόσπορος, Bósporos (bós. po. ros); Turkish: İstanbul Boğazı, (isˈtanbuɫ bo ‿ aˈzɯ)) is a narrow, natural strait and an internationally significant waterway located in northwestern Turkey . It forms part of the continental boundary between Europe and Asia, and separates Asian Turkey from European Turkey . The world's narrowest strait used for international navigation, the Bosporus connects the Black Sea with the Sea of Marmara, and, by extension via the Dardanelles, the Aegean and Mediterranean seas . </P> <P> Most of the shores of the strait are heavily settled, straddled by the city of Istanbul's metropolitan population of 17 million inhabitants extending inland from both coasts . </P>

What is the strait between the black sea and the sea of marmara