Ubsunur Hollow (also spelled Uvs Lake Basin; Mongolian: Увс нуурын хотгор) is a fragile mountain endorheic basin or depression located on the territorial border of Mongolia and the Republic of Tuva in the Russian Federation, named after Uvs Lake, a large, shallow and very saline lake in the basin's center. Several smaller lakes are scattered throughout. It is part of a combination of raised lands and depressions located throughout the Tannu-Ola and Altai mountainous regions. Here, the world's most northern desert meets the northern hemisphere's most southern tundra zone. The Ubsunur Hollow was inscribed on the World Heritage Site in 2003. The total area of Uvs Lake drainage basin is 70,000 km². The greater part of it lies in Mongolia (Khövsgöl, Zavkhan and Uvs Provinces), and the northern part in Russia (Tuva).
Ubsunur Hollow's importance lies chiefly in its cultural heritage and it is the most important place in Central Asia for its concentration of unstudied archeological artifacts, especially its burial mounds, rock carvings, and stone sculptures, which are remnants of medieval settlements and Buddhist temples. There are as many as 20,000 burial mounds, many of them being older than the Egyptian pyramids. Ubsunur Hollow was nominated as a World Heritage Site in 1995 as "one of the largest intact watersheds in Central Asia where 40,000 archaeological sites can be found from historically famous nomadic tribes such as the Scythians, the Turks and the Huns."
The hollow is located on the border between Mongolia and Russia and has an area of just over 10,000 km². The terrain encompasses a wide variation of climates, including glaciers, alpine tundra, sub-alpine meadows, and vast mountain taiga areas. There are also forested steppes, treeless steppes, semi-arid deserts, and ever-shifting sand dunes. It is a scenic and highly diversified natural habitat. Due to its location on the cusp of the Siberian and Central Asian-Mongolian terrains, the flora and fauna of the hollow exhibit a high biodiversity for mid-latitudes. Animal species that inhabit both mountains and tundra, such as the Siberian roe deer, and Altai snowcock, flourish here.
The endangered snow leopard is also present, as well as taiga dwellers such as the Caspian red deer, lynx and wolverine. Steppe dwellers include the Mongolian lark, demoiselle crane and long-tailed Siberian squirrel. Desert inhabitants include the bustard and midday gerbil. The bird species alone number some 359. Since the hollow is a protected area, many ancient species extinct in other regions have found refuge here.