His anthropological field research since 1980 has primarily focused on the Incas and sacred landscape in Argentina, Bolivia, Chile, Ecuador, and Peru.

[4] 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: the Raute and Kusunda.

While in Nepal, he also directed Peace Corps Training Projects and was a member of teams that made some of the first rafting descents of Trisuli and Sun Kosi rivers.

In 1965 and 1967, he was also a member of teams which undertook nautical archaeological research of Roman shipwrecks in the Mediterranean Sea off southern Italy and of an Iron Age Villanovan village in a northern Italian lake (Lago di Bolsena) in 1965.

His interest in the Iceman led to his study in recent years of the role of sacred landscape in Neolithic religion in the central Alps.

Johan first began mountain climbing in 1964 in the Alps and in the mid-1970s in the Himalayas, including participating on the successful 1976 American Everest Expedition and making a first ascent in 1979 of the South Face of Buni Zom (21,500 ft) in the Hindu Kush (Pakistan).

He has investigated traditional religious beliefs and climbed sacred mountains in Greece in 2002, in Bali, Indonesia during 2007, and in Venezuela, Mongolia, and the Holy Land (Israel) in 2012.

He directed teams that recovered four Inca human sacrifices on Ampato (20,708 ft) in southern Peru, including the Mummy Juanita (the "Ice Maiden").

[6] In 1995 and 1999 Time selected Dr. Reinhard's finds as among “the world's ten most important scientific discoveries” of those years—making him one of the few scientists to have had his research chosen twice for this recognition.