The lake has an area of 54.4 km2, a maximum length of 13 km, width 8 km and depth 3.6 m. The bottom of the lake is covered with thick layer of silt sapropel (a sort of ooze used as fertilizer and for other purposes).

The first people settled at the lake 6 thousand years ago.

It is historically certain that the Merya people had their capital in Sarskoe Gorodishche on the southern shore of the lake.

They named the lake Nero (meaning "silty", "marshland")[4][5] or Kaovo ("place where gulls live").

The first steamboat Emel’yan (Russian: Емельян) appeared on the Lake in 1883.