The Ilmensee (Russian Ильмень Озеро, Ilmen Ozero, Ukrainian Ільмень Озеро, Ilmen Ozero, Finnish Ilmajärvi ) is a lake in north-western Russia between Moscow and Saint Petersburg. On Ilmensee lies the ancient city of Novgorod. Its water surface varies greatly 730-2090 km ². The maximum water depth usually varies accordingly between 2.35 m and 5.8 m. The lake lies at an altitude of about 18 m. Outflow is the Volkhov, which flows into Lake Ladoga after 224 kilometers.
Southeast of Lake Ilmen about 100,000 German soldiers were almost a year surrounded by the Red Army in Demyansk pocket in World War II since the beginning of 1942. Military Strategically, the successful retreat of the German troops was some historians believes contributed to some miscalculations in the matter of supply and relief in the subsequent Battle of Stalingrad.