It rises in the Valdai Hills of Russia, 225m above sea level north-west of Moscow. The Kama, Oka, Vetluga and the Sura are its main tributaries. The Volga and its tributaries form the Volga river system, which drains an area of about 1.35 million square kilometres in Russia. The Volga Delta has a length of about 160 kilometres. It includes 