Black Sea
The Black Sea is a body of saltwater that is between the Ukraine, Russia, Romania, Turkey, and Bulgaria. It is a pocket of the Mediterranean, and passes through a narrow straight next to Constantinople, the Bosphorus, to the Sea of Marmara, and then again through the Dardanelles.
The ancient Greeks had colonies around the Black Sea. Communities in the Trebizond area survived until the early 20th century.