One of the world's most strategic waterways, Bosphorus is a natural strait between the Black Sea and the Sea of Marmara; it is an inundated valley that follows an irregular northeast-southwest course 32 kilometers (20 miles) long, 730-3300 meters (800-3600 yards) wide, 30-120 meters (100-395 feet) deep.
Bosphorus comes from a Tracian word of unknown origin, interpreted in Greek as meaning "Ford of the Cow", from the legend of "Io", one of the many lovers of Zeus, who swam across the sea here as a cow chased and continuously disturbed by flies sent by Hera.
Known in Turkish as Bogazici (the Strait), it links the Black Sea with the Sea of Marmara and, with the Dardanelles Strait (in Canakkale), separates Europe from Asia. It is a former river valley which was drowned by the sea at the end of the Tertiary period. This is a very busy strait with many commercial ships and oil tankers, as well as local fishing and passenger boats. The current flows from north to south; however, a strong subsurface countercurrent with numerous points and coves sets up swirls and eddies that make navigation dangerous to the inexperienced.
There are three suspension bridges over the Bosphorus Strait, all of them with a toll:
The first bridge is streching between Beylerbeyi neighbourhood on the Asian side and Ortaköy neighbourhood on the European side. It was opened in October 1973 and was called as "Bogazici (Bosphorus) Bridge", then in July 2016 it's named as "Martyrs of July 15th" dedicated to the victims died during the failed coup attemp of 15th of July 2016. It's 1074 meters (1175 yards) long, has 6 lanes, 64 meters (210 feet) high from the water, and 165 meters (540 feet) high pillars.
The second bridge streches between Anadolu Hisari and Rumeli Hisari. It was opened in July 1988 and is called as "Fatih Sultan Mehmet Bridge" (abv. FSM). It's 1090 meters (1192 yards) long, has 8 lanes, 65 meters high from the water.
The third bridge is located at the entrance from the Black Sea, streching between Garipçe village on the European side and Poyrazköy village on the Asian side. It was inagurated in August 2016 and called as "Yavuz Sultan Selim Bridge" (abv. YSS). It's 1408 meters (1540 yards) long between two pillars, 59 meters (65 yards) wide with 8 lanes + 2 rail lines, and 322 meters (1056 feet) high pillars, one of the biggest suspension bridges in the world.
There are also two tunnels under the Bosphorus:
The first one is called "Marmaray", which was opened in October 2013. This tunnel is for the subway system only. The section under the water is 1400 meters (1531 yards) long, between Uskudar and Sirkeci neighborhoods.
The second tunnel opened in December 2016. It's called "Eurasia Tunnel" and is for motor vehicles only, paying a toll. It's partly under the Bosphorus but mostly under the Sea of Marmara. The section under the water is 5400 meters (5905 yards) long between Haydarpasa and Ahirkapi neighborhoods, and it has two levels for separate driving directions.
A couple of more tunnels are planned to be built under the Strait in the future.
With the shores rising to heights up to 200 meters (650 feet), lined with palaces, ruins, villages, and gardens, this is one of the most beautiful stretches of scenery in Turkey. The best way of seeing the Bosphorus in all its beauty is to take a trip on one of the coastal boats, in this way you can also admire many of the old Ottoman wooden houses (called as Yali in Turkish). You can also stay in some of the best hotels or eat in some of the best restaurants along its shores during your stay in this magnificent city.
Some of the interesting palaces, buildings or neighborhoods along the Bosphorus are: Galata tower, Dolmabahce Pkalace, Ciragan Palace, Yildiz Palace, Besiktas, Ortaköy, Arnavutköy, Bebek, Rumeli Fortress, Tarabya, Yeniköy, Istinye, Sariyer, Uskudar, Kanlica, Beykoz, Anatolian Fortress, Kuzguncuk, Beylerbeyi Palace, and Kuleli former Military High school.