Caspian Sea

The Caspian Sea is the largest inland body of water on Earth, an endorheic, brackish basin covering about 371,000 square kilometers between the Caucasus Mountains, the Central Asian steppe, southern Russia and the Iranian plateau, bordered by Kazakhstan, Russia, Azerbaijan, Iran and Turkmenistan. Its southern basin plunges past 1,000 meters, the third deepest depression on Earth outside the open ocean, while its salinity of roughly 1.2 percent is about a third that of seawater. The sea supports endemic sturgeon populations prized for caviar and the Caspian seal, the only marine mammal found nowhere else. Decades of oil extraction around its shores have made pollution a persistent threat to its ecology.