The Baliem Valley, also spelled Balim Valley and sometimes known as the Grand Valley, of the highlands of Western New Guinea, is occupied by the Dani people. The main town in the valley is Wamena. The valley is about 80 km in length by 20 km in width and lies at an altitude of about 1,600-1,700 m, with a population of 100,000.
As far as the outside world was concerned, the discovery of the Baliem Valley and the unexpected presence of its large agricultural population was made by Richard Archbold’s third zoological expedition to New Guinea in 1938. On 21 June an aerial reconnaissance flight southwards from Hollandia (now Jayapura) found what the expedition called the ‘Grand Valley’. Since then the valley has gradually been opened up to a limited amount of tourism.
The following is copied from the back cover of Peter Matthiessen’s book Under the Mountain Wall:

“In the Baliem Valley in Central New Guinea live the Kurelu, a Stone Age tribe that survived into the twentieth century. Peter Matthiessen visited the Kurelu with the Harvard-Peabody Expedition in 1961 and wrote Under the Mountain Wall as an account not of the expedition, but of the great warrior Weaklekek, the swineherd Tukum, U-mue and his family, and the boy Weake, killed in a surprise raid. Matthiessen observes these people in their timeless rhythm of work and play and war, of gardening and wood gathering, feasts and funerals, pig stealing and ambush. Drawing on his great skills as naturalist and novelist, Matthiessen offers a remarkable firsthand view of a lost culture in all its simplicity and violence — on the brink of incalculable change.”