Ulaanbaatar is located at about  above mean sea level, slightly east of the centre of Mongolia on the Tuul River, a sub-tributary of the Selenge, in a valley at the foot of the mountain Bogd Khan Uul. Bogd Khan Uul is a broad, heavily forested mountain rising  to the south of Ulaanbaatar. It forms the boundary between the steppe zone to the south and the forest-steppe zone to the north.