Black Sea

The Black Sea is a body of water unlike any other: beneath a thin, living surface layer lies the largest mass of oxygen-free water on Earth, a dark abyss where almost nothing can survive. Hemmed in by Europe and Asia and connected to the wider ocean only through the slender Bosphorus, it is fed by some of the continent's greatest rivers. Its name, ancient and ominous, may come from the colour of its storm-darkened depths or from its forbidding reputation among early Greek sailors.

Covering about 436,400 square kilometres and reaching some 2,212 metres at its centre, the Black Sea is sharply stratified. Heavy rivers — the Danube, Dnieper, and Don — flood it with fresh water that floats atop denser, saltier inflow from the Mediterranean, and the two layers barely mix. Below roughly 150 metres the water is anoxic and rich in hydrogen sulphide, a chemistry that has preserved ancient shipwrecks in extraordinary condition. The basin connects southward through the Bosphorus, Sea of Marmara, and Dardanelles to the Aegean and Mediterranean.

Greek colonists ringed these shores from the seventh century BC, drawn by grain and fish, and the sea became a cultural meeting point of Hellenic, Scythian, Byzantine, Ottoman, and Slavic worlds. Its waters have long been strategically coveted, controlling access between Russia, Turkey, and the Mediterranean. Today six nations share its coast, and it remains a flashpoint of geopolitics as well as a sea under severe ecological strain from nutrient pollution and overfishing.

• Asia
  Earth's largest and most populous continent borders
• Mediterranean Sea
  The cradle sea of Western civilization, locked between three continents connects to
• Danube
  Europe's second river, flowing through ten countries feeds from
• Europe
  A small, intricate continent of outsized influence located on
• Volga River
  Europe's longest river and the soul of Russia nearby