The Caspian Sea is the world’s largest lake by surface area, despite being commonly called a sea.
The Caspian covers roughly 371,000 square kilometres and has no natural outlet to the world’s oceans. Its name reflects its immense size and the long-standing geographic tradition of calling it a sea, but its enclosed basin makes it a lake in many geographical classifications. It is bordered by Russia, Kazakhstan, Turkmenistan, Iran and Azerbaijan.
The Caspian is saline, although its salinity varies considerably from north to south. The northern basin is shallow and receives major river inflows, especially from the Volga, while the southern basin is much deeper. The lake’s water level has changed substantially over historical and modern times. It supports important fisheries, including sturgeon associated with caviar production, and contains major oil and natural-gas resources. The nearby Aral Sea is a separate inland body that suffered severe shrinkage after large-scale river diversion.