Dardanelles. Satellite image of the Dardanelles (centre) in northwestern Turkey, a 61 kilometre long strait that separates European Turkey (top) from Asiatic Turkey (bottom). North is at top. The maximum width is 7 kilometres and in the area known as the Narrows, the distance is no more than 1,600 metres. It is a vital transportation route between the Black sea and the Mediterranean Sea, connecting the Aegean Sea (left) to the Sea of Marmara (where the strait opens up at far right).