The Bosporus or Bosphorus Strait is a natural strait and an internationally significant waterway located in Istanbul, Turkey. The Bosporus connects the Black Sea to the Sea of Marmara and forms one of the continental boundaries between Asia and Europe. It also divides Turkey by separating Asia minor from Thrace. It is the world's narrowest strait used for inte…The Bosporus or Bosphorus Strait is a natural strait and an internationally significant waterway located in Istanbul, Turkey. The Bosporus connects the Black Sea to the Sea of Marmara and forms one of the continental boundaries between Asia and Europe. It also divides Turkey by separating Asia minor from Thrace. It is the world's narrowest strait used for international navigation.