The strategic strait of Bosporus (in Turkish: Istanbul Boğazi) in northwest Turkey divides Europe from Asia, while it links the Sea of Marmara (Propontis) to the Black Sea. With a length of almost 32 kilometers and a maximum width of 3.4 kilometers, it is the narrowest strait in international navigation.
Its name derives from the words βοῦς (ox) and πόρος (passage) and is related to the following myth: when Hera discovered the romantic affair of Zeus and Io, daughter of the king of Argos and priestess of the goddess’ temple, he transformed her in a white cow so as to protect Io from the goddess’ rage.
Soon after Hermes killed Argos, to whom Hera had assigned the cow’s protection, the goddess sent a gadfly (οἶστρος) to the transformed girl in order to torture her. Thus, after running along the shores of the Ionian Sea (its name comes from this incident), Io crossed the strait of Bosporus and wandering in Minor Asia, she ended up in Egypt where she gave birth to the son of Zeus, Epaphus. She became human again, reigned and finally was worshipped under the name of Isis.
The limits of Bosporus are defined by the capes of Sarayburnu (south) and Rumelifeneri (north) on the European coast and by the capes of Kavakburnu (south) and Anadolufeneri (north) on the Asian. On its north exit to the Black Sea, according to the legend, there were the Symplegades/Crashing Rocks, which after the passing of the Argonauts, stopped moving forever. In the strait two opposite currents flow, making it difficult for the ships to pass.
The first attempt to link the strait is dated in 513 B.C., when the Samian architect Mandrocles constructed, under the orders of Darius I (521-486 B.C.), a bridge at the locations of Rumeli Hisar (European coast) and Anadolu Hisar (Asian coast), in order for the Persian army to pass.
Today, three are the bridges that connect the coasts of Bosporus. The first was built in 1973 and its length is 1.074 m. Five kilometers to the north and in 1988, the bridge Fatih Sultan Mehmet, with a length of 1.090 m., was completed. The construction of the third bridge started in 2013 and finished in 2016. Its length of 2.164 m. connects the most northern parts of the strait, south of the residential areas of Garipçe and Poyrazköy.
From December 2016, one can cross the Bosporus also by the subterranean tunnel Avrasya Tüneli (Eurasia Tunnel), 5 kilometers long, between Kumkapi and Koşuyolu. In addition, underneath Bosporus traverse almost 1.400 m. of the Marmaray undersea railway tunnel, which from 2013 connects the historical center of Constantinople to Üsküdar on the Asian coast.
In the byzantine period, many settlements lied on the shores like Diplokionion, Daphne, Hagios Mamas and Panteichion. These days in this populous area, one can see many ottoman palaces, among them the famous Dolmabahçe and Yildiz, and even mosques, museums, universities like the one of Bosporus
(Boğazici Universitesi) and of course the noted luxurious residences (yali).