The Dardanelles , formerly known as Hellespont , is a narrow strait in northwestern Turkey connecting the Aegean Sea to the Sea of Marmara. It is one of the Turkish Straits, along with its counterpart, the Bosphorus. It is located at approximately 40°13â²N 26°26â²E 40.217°N 26.433°E 40.217; 26.433. The strait is 61 kilometres long but only 1.2 to 6 kilometres wide, averaging 55 metres deep with a maximum depth of 103 metres . Water flows in both directions along the strait, from the Sea of Marmara to the Aegean via a surface current and in the opposite direction via an undercurrent.