The largest lake in the world — the Caspian Sea, is located on the mainland depression, on the border of two major parts of the Eurasian continent. It is also the largest indoor water system on our planet.‚Äč

The most ancient inscriptions related to the Caspian Sea were encountered upon an Assyrian ceramic pot, mentioned as the Southern Sea. The Hekatey of Milet's historical and geographic books (VI BC) mentioned this sea as Kaspi and Hirkan. The first ethnic name is associated with the name of the Kaspi people who were dwelling in the southwest coastal areas of the current territory of Azerbaijan. Its second name was originated from Hircan country, which was located in the southeast coastal areas (translated from Persian as "the country of wolves"). These two names of the Caspian Sea were also mentioned by Herodotus (5th century BC). Other ancient authors were also using such names as Alban (in association with the Albanian ethnic name), Stormy and Hirkan names of the sea. Ancient Russian manuscript sources named the Caspian Sea as Goy (that means Blue in Mongolian-Turk languages), Kharezm (in association with the Kharezm power located within the area extended from Amu-Darya River lower intercourse up to the Caspian Sea, Khvalin, Darband, etc. People that had dwelt around the Caspian Sea called it with different names, for example, the Russians Khvalin, the Tartars — Agh Deniz (White Sea), the Turk people  Kichik Deniz (Small Sea), the Chinese people — Si Hay, and the New west Sea. Venice Ambassador to Iran (1474-1477) A. Kontarini named it as Baku Sea. The Russians used to call the sea Caspian since the 16th century. Other countries around the Caspian Sea called this basin as follows: Caspian (Khazar) in Azerbaijan, (Khazar -Turk speaking people that dwelt within the northwest coastal areas during V-X centuries), Mazandaran — in Iran, as well as Caspian — in Kazakhstan and Turkmenistan. All in all, over 70 names were given to the Caspian Sea by various people who dwelt around the basin at various times.