Nevado de los Patos, Second Ascent. Swiss climber Louis Glauser and I spent several weeks doing mountaineering combined with high-altitude archaeological research. We began in Christmas 1984 in the Chilean side of the Puna. We first explored the north and east sides of Llullaillaco, looking for a reported high altitude cemetery, which we failed to locate, but we did find new archaeological sites. We then entered the Argentinian side of the Puna (see above), to continue our activities and in late March 1985 we returned to Chile. We made the following ascents: Volcán Copiapó (6052 meters, 19,855 feet), March 21; Nevado de los Patos (6250 meters, 20,506 feet), whose main summit is wholly within Argentinian territory, March 27, a second ascent; and Peña Blanca (6019 meters, 19,748 feet), the 29th. I next ascended El Ermitaño (6146 meters, 20,165 feet), while Glauser climbed Ojos del Salado (March 29). In early April we drove north. We climbed Doña Inés (5073 meters, 16,645 feet), on April 1, Llullaillaco (6739 meters, 22,110 feet), the 10th., where we found archaeological sites already sacked, and nearby Cerro Chuculai (5416 meters, 17,770 feet), where we observed rather humble ruins. Reaching still farther north, nearing the Chilean-Bolivian border, we climbed Pabellón del Inca (5110 meters, 16,765 feet), April 17, Pumiri (4907 meters, 16,100 feet) the 22nd., and Tata Sabaya (5385 meters, 17,666 feet), the next day.