The Altai-Sayan Ecoregion encompasses a mountain system surrounded by steppes in the north and east and by deserts and semi-deserts in the south and west. It is located in the transition zone between the great northern taiga forests of central and Eastern Siberia, the steppes of western Siberia, the Altai Mountains and the deserts of China and Mongolia. The region includes the Altai and Sayan mountain systems and vast intermountain depressions. The Altai Mountains extend along the Russian-Kazakhstan border in the northwest and to the Chinese-Mongolian border in the southwest. The Western and Eastern Sayan Mountains extend toward the east from the Altai Mountains to nearly the southern tip of Lake Baikal. The Altai-Sayan Mountains are extremely rugged with rich forests stretching high into the mountain valleys and glaciers in the higher valleys.