It leads from the Aegean Sea to the Sea of Marmara and then through the Bosphorus strait to the Black Sea.Thus the Dardanelles is the outer gateway to a great productive area. The world's ships must pass through here to reach the grain ports of Ukraine and the oil ports of Romania and the Caucasus region. The western side of the strait is formed by the Gallipoli peninsula. Major ports along its shores are Gallipoli, Eceabat, and Canakkale; and many famous castles like Kilitbahir built in 1452 by the Ottoman sultan Mehmet II, stand along its banks. Also, famous Turkish sailor and the first Turkish marine cartographer Piri Reis was born in Gelibolu town.