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.
Baku–Tbilisi–Ceyhan pipeline
The Caspian Sea lies above one of the world's largest collections of oil and gas fields. As the sea is landlocked, transporting oil to Western markets is complicated. During Soviet times, all transportation routes from the Caspian region were through Russia. The collapse of the Soviet Union inspired a search for new routes. Russia first insisted that the new pipeline should pass through its territory, then declined to participate.