The Bosphorus is approximately 30 km long, and at its narrowest point the Anadolu and Rumeli fortresses face each other across it. Here the width of the strait is about 800 meters. On the surface, the Bosphorus flows like a river from the Black Sea to the Marmara. This current gets much stronger and becomes truly dangerous around the fortresses. Below the surface current, there is another current flowing in the opposite direction. These currents have always constituted a threat for the ships crossing the strait. The Bosphorus is like a narrow valley and it has an average depth of 50 and a maximum depth of 110 meters. Because of the currents and the different temperatures on various levels, the Bosphorus is a paradise for fish. The fish migrate between the Black Sea and the Marmara according to the season. These fish, peculiar to these waters, are caught during the migration seasons. Nowhere else can one find such fine-tasting fish. Until recent times, the settlements along the Bosphorus were quite limited due to the strong currents and the lack of roads. They consisted of a few villages, some imperial palaces and the mansions of the wealthy. In the 19th century the embassies started to build their summer residences here. Today the shores and the hills are developing as residential districts. There are numerous fish restaurants and cafes on both sides of the Bosphorus. Modern villas intermingle with the relatively few old wooden seaside mansions that have been preserved. One of the most beautiful sights in the world, the Bosphorus is a strait winding between two continents and joining two seas. The Black Sea is connected to the Aegean through the Bosphorus and the Dardanelles. It offers a different beauty each season, and in spring it is adorned with the pink flowers of the Judas trees.

The entrance to the Bosphorus is like a small bay, and from here one gets the best view of the old town. The rest of the 30 km long waterway is like a series of lakes. It is only from the air that one realizes it is a strait. The first bridge across the Bosphorus was completed in 1973, and the second, the Fatih (Mehmet the Conqueror) bridge in 1988. There are plans for building either a third bridge over or a tunnel under the strait. The settlements on the shore grew quickly after 1852 when steamboats were put into service here, and over time they became included in the city boundaries. The ancient name of "Bosphorus" means "Cow Passage". As a passage that can be traversed easily, it has facilitated the spread of civilizations between Asia and Europe and the development of trade and other relations. In the 2,500 year history of the city, the Bosphorus, its extension the Golden Horn and the historical peninsula have always been coveted places, and they witnessed numerous military campaigns and mass migrations. The earliest mention of the Bosphorus in mythology is in the story of the Argonauts who sail through the strait to the Black Sea. It is known that in 6th century BC the Persian armies tied their boats together for easier passage, thus forming the first bridge over the Bosphorus. Some of the noteworthy buildings on the European shore are the Ciragan Palace, which was restored and converted into a hotel, the former Feriye Police Station which is now used as a cultural center, and the Ortakoy Mosque and square. New five star hotels and tall buildings are springing up on the hills this side of the Bosphorus.