The Bosporus or Bosphorus, also known as the Istanbul Strait, (Turkish: Bogaz or Bogazici) is a strait that forms the boundary between the European part (Rumelia) of Turkey and its Asian part (Anatolia). Its English name comes from a Greek legend: Zeushad an affair with a beautiful women named Io. When Hera, his wife, discovered his infidelity, she turned Io into a cow and created a horsefly to sting her on the rump. Io jumped clear across the strait. Thus bous=cow, and poros=crossing-place: Bosporus= “crossing-place of the cow.”
Bosporus is the world’s narrowest strait used for international navigation. It connects the Black Sea with the Sea of Marmara, which is connected by the Dardanelles to the Aegean Sea, and thereby to the Mediterranean Sea. It is approximately 30 km long, with a width of changing between 700 and 3700 meters. The depth varies from 36 to 124 metres in midstream.
The shores of the strait are heavily populated as the city of Istanbul with a metropolitan area in excess of 15 million inhabitants straddles it.
Two bridges cross the Bosporus named the Bosphorus Bridge and Fatih Sultan Mehmet (Bosphorus II) bridge.