 During 1989–1992 he directed an underwater archaeological research project in Lake Titicaca, the world’s highest navigable lake (12,500 ft), that resulted in the discovery of rare Inca and Tiahuanaco (pre-Inca) artifacts.He has lived more than ten years in the Himalayas, conducting anthropological research primarily in Nepal, but he has also undertaken investigations in Tibet, Bhutan, Sikkim, and the Garhwal Himalaya.His studies in Nepal included culture change among the Raji of nomadic hunter-gatherers to settled agriculturalists; Himalayan shamanism; the role of sacred mountains in Tibetan Buddhism and Hinduism; the sacred "hidden lands" of Tibetan Buddhism (seven of which he has explored); and two of the world's last nomadic hunting and gathering tribes