Nevado Sajama dominates the park not just vertically but psychologically. At 6,542 meters, it is the highest point in Bolivia, a stratovolcano whose snow-capped summit is visible from extraordinary distances across the flat altiplano. The park's altitude ranges from 4,200 to 6,500 meters, with the village of Sajama sitting at 4,240 meters. Non-guided hiking trails reach 5,000 meters, and guided treks extend to 5,600 meters and beyond for those attempting the summit. The landscape shifts between extremes -- vast, rolling grasslands where the wind bends the ichu grass in long waves, then sudden eruptions of volcanic rock, then wetlands that seem impossible in such dry air. Hot springs and geysers punctuate the valleys, evidence of the geological forces that built this terrain and continue to reshape it.

The wildlife catalog reads like a field guide to Andean adaptation. Viscachas -- chinchilla relatives with curled tails -- perch on sun-warmed rocks. Herds of vicunas, llamas, and alpacas move across the grasslands in shifting formations, their movements the only animation in an otherwise still landscape. Horned coots wade in the shallow lakes. Less commonly spotted are pumas, Andean cats, and armadillos, animals whose presence is inferred more often from tracks than from sightings. Overhead, Andean condors soar on thermals, and pink flamingos stand in the shallows with the geometric stillness that makes them look like lawn ornaments until one lifts a leg. Rheas -- South America's version of the ostrich -- appear occasionally on the open plains. Hummingbirds, improbably, dart among the scrub at altitudes where flight should cost more calories than it delivers.

Sajama's appeal is precisely what most tourist destinations try to eliminate: emptiness. The park does not experience the crowds that overwhelm other Bolivian natural attractions. Trails lead across open plains where the horizon is unbroken and the distance between you and the nearest other human being can be measured in kilometers. The recommended approach is straightforward -- walk in whichever direction interests you, using the same paths that llamas and alpacas have worn across the grassland. The most direct route is usually the best one. Several longer treks require guides and proper mountaineering equipment, particularly any approach to Nevado Sajama's summit. Temperatures drop below freezing most nights from March onward, and the combination of altitude, wind, and cold demands preparation. But the reward is a landscape that functions as a walking meditation, where the quiet is deep enough to hear the blood in your own ears.

Sajama village, at 4,240 meters, serves as the park's base. It offers budget accommodations of varying comfort, small stores stocked with basic supplies, and restaurants serving standard Bolivian fare. The entrance fee is 100 bolivianos, collected at a gate about one kilometer from the highway junction. Most travelers arrive from Patacamaya, 190 kilometers and two hours to the east, on a daily minibus that departs around noon and returns at 5:30 a.m. Others come through Tambo Quemado, the Bolivian border town facing Chile, where transport to the village can be arranged for 10 bolivianos -- or you can simply walk the 15 kilometers across the open plain, which is, as one travel writer noted, probably what you came here for. The park shares a border with Chile's Lauca National Park, and the two protected areas form a continuous corridor of high-altitude wilderness that ignores national boundaries with the same indifference that the condors do.