In eastern Central Asia between the southern flank of the Tien Shan mountains and the northern edge of the Pamir range is Irkeshtan Pass, at 9,400 feet in elevation, the southern Silk Road route, which of course was impassable before circa 1400 b. c. during the Ice Age but since then the route from the ancient city of Osh, founded circa 1300 b. c. when the route opened up to East Asia at Kashgar, in the Tarim basin which was verdant during the Ice Age now a desert.
