Caspian Sea
The Caspian has characteristics common to both seas and lakes. It is often listed as the world's largest lake, although it is not a freshwater lake. It contains about 3.5 times more water, by volume, than all five of North America's Great Lakes combined. The Caspian was once part of the Tethys Ocean, but became landlocked about 5.5 million years ago due to plate tectonics. The Volga River (about 80% of the inflow) and the Ural River discharge into the Caspian Sea, but it has no natural outflow other than by evaporation. Thus the Caspian ecosystem is a closed basin, with its own sea level history that is independent of the eustatic level of the world's oceans.
Landlocked country
Several countries have coastlines on landlocked seas, such as the Caspian and the Dead. Since these seas are in effect lakes without access to wider seaborne trade, countries such as Kazakhstan are still considered landlocked. Although the Caspian Sea is connected to the Black Sea via the man-made Volga–Don Canal, large oceangoing ships are unable to traverse it.