Pamir (pəmērˈ, pä–) [key] or Pamirs, mountainous region of central Asia, located mainly in Tajikistan and extending into NE Afghanistan and SW Xinjiang Uygur Autonomous Region, China; called the "roof of the world." Many peaks rise to more than 20,000 ft (6,096 m); Ismoili Somoni Peak (24,590 ft/7,495 m) and Lenin Peak (23,508 ft/7,165 m) are the Pamir's highest. The region forms a geologic structural knot from which the great Tian Shan, Karakorum, Kunlun, and Hindu Kush mountain systems radiate. Snowcapped throughout the year, the Pamir experiences long cold winters and cool summers. Annual precipitation is c.5 in. (12.7 cm), which supports grasslands but few trees. Several large glaciers, including the 144-mi-long (231-km) Murghab Valley glacier, are in the Pamir. Coal is mined in the W Pamir, but nomadic sheep herding in the upland meadows is the main economic activity. Terek Pass, used by Italian traveler Marco Polo on his way to China in 1271, is one of several high passes used by routes passing through the Pamir. The French explorer Pierre Bonvalot made the first European north-south crossing of the Pamir in 1886.