The Volga is the longest river in Europe. Situated in Russia, it flows through Central Russia to Southern Russia and into the Caspian Sea. The Volga has a length of 3,531 km (2,194 mi), and a catchment area of 1,360,000 km2 (530,000 sq mi). It is also Europe's largest river in terms of average discharge at delta – between 8,000 m3/s (280,000 cu ft/s) and 8,500 m3/s (300,000 cu ft/s) – and of drainage basin. It is widely regarded as the national river of Russia. The hypothetical old Russian state, the Rus' Khaganate, arose along the Volga c. 830 AD. Historically, the river served as an important meeting place of various Eurasian civilizations.

An endorheic basin is a drainage basin that normally retains water and allows no outflow to other, external bodies of water ; instead, the water drainage flows into permanent and seasonal lakes and swamps that equilibrate through evaporation. Endorheic basins are also called closed basins, terminal basins, and internal drainage systems.