Khustain Nuruu National Park, whose name means "the birch range", lies 90 km southwest of the capital at an elevation of 1,843 meters in Altanbulag sum. It is bordered to the west by Avdar Mountain.

This natural reserve, established in 1992, originally covered 506 km² before becoming a national park in 1998 (now 500 km²) with the primary mission of reintroducing Przewalski's horses, locally called takhi, and protecting the forest steppe ecosystem, which faces severe threat from overexploitation of the land. The park is home to 459 plant species, 85 lichen species, 90 moss species, 33 fungal species, and 44 mammal species including red deer, Mongolian gazelle, roe deer, grey wolf, lynx, and red fox. Additionally, the park hosts 217 bird species including golden eagles, bearded vultures, great bustards, whooper swans, black storks, and partridges. The reserve encompasses both desert and mountainous terrain.