The highlands of SW Bolivia, NW Argentina, and N Chile are the most arid part of the Andes. In this area, opportunities for human settlement concentrate in deep river valleys, piedmont oases, and to the lowest basins of the Altiplano (highplateau). This environmental structure has resulted in a long-term pattern of discontinuous settlement, with relatively small populations concentrated in favorable areas, separated by vast expanses of unpopulated mountain heights and deserts.
