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.
Absheron Peninsula
It extends eastward into the Caspian Sea, and reaches a maximum width of . Though technically the easternmost extension of the Caucasus Mountains, the landscape is only mildly hilly, a gently undulating plain that ends in a long spit of sand dunes known as Shah Dili, and now declared the Absheron National Park. In this part the peninsula is dissected by ravines and characterized by frequent salt lakes.