The Black Sea is an inland sea bounded by Europe, Anatolia and the Caucasus and is ultimately connected to the Atlantic Ocean via the Mediterranean and Aegean Seas and various straits. The Bosporus strait connects it to the Sea of Marmara, and the strait of the Dardanelles connects it to the Aegean Sea region of the Mediterranean. These waters separate eastern Europe and western Asia. The Black Sea also connects to the Sea of Azov by the Strait of Kerch.

The Black Sea has an area of 436,400 km2 (168,495.0 sq mi), a maximum depth of 2,206 m (7,238 ft), and a volume of 547,000 km³ (133,500 cu mi). The Black Sea forms in an east-west trending elliptical depression which lies between Bulgaria, Georgia, Romania, Russia, Turkey, and Ukraine. It is constrained by the Pontic Mountains to the south, the Caucasus Mountains to the east and features a wide shelf to the north-west. The longest east-west extent is about 1,175 km.

Important cities along the coast include: Constanţa (306,000 with a metropolitan area of 550,000), Istanbul (11,372,613), Odessa (1,001,000), Mangalia (41,153), Burgas (229,250), Varna (357,752), Kherson (358,000), Sevastopol (379,200), Yalta (80,552), Kerch (158,165), Novorossiysk (281,400), Sochi (328,809), Sukhumi (43,700), Năvodari (34,669), Poti (47,149), Batumi (121,806), Trabzon (275,137), Samsun (439,000) Ordu (190,143) and Zonguldak (104,276).

The Black Sea has a positive water balance, which results in a net outflow of water 300 km³ per year through the Bosphorus into the Aegean Sea (part of the Mediterranean Sea). Mediterranean water flows into the Black Sea as part of a 2-way hydrological exchange. The Black Sea outflow is less saline and cool, and therefore floats over the warm, more saline Mediterranean inflow. The Black Sea also receives river water from large Eurasian fluvial systems to the north of the Sea, of which the Don, Dnieper and Danube are the most significant.

Sources : Wikipedia