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.
Europe
The prevalent definition of Europe as a geographical term has been in use since the mid-19th century.
Europe is taken to be bounded by large bodies of water to the north, west and south; Europe's limits to the far east are usually taken to be the Urals, the Ural River, and the Caspian Sea; to the southeast, including the Caucasus Mountains, the Black Sea and the waterways connecting the Black Sea to the Mediterranean Sea.