The Altiplano, Spanish for high plain, is the most extensive area of high plateau on earth outside of Tibet. It is an area of inland drainage lying in the central Andes and lies where the Andes are at their widest. The Altiplano occupies parts of Chile, Argentina, Bolivia, and Peru. Its height averages about 3,300 meters (11,000 feet), somewhat less than that of Tibet. Unlike the Tibetan plateau, however, the Altiplano is dominated by the massive peaks of active volcanoes to the west. The Atacama Desert, the driest area on the whole planet, lies to the southwest of the Altiplano.
At the end of the Pleistocene epoch, the whole extent of the Altiplano was covered by a vast lake, Ballivián, the present remnants of which are Lake Titicaca, straddling the border between Peru and Bolivia, and Poopó, a saline lake which extends south of Oruro, Bolivia. Salar de Uyuni and Salar de Coipasa are two large dry salt flats which also formed after the Altiplano paleolakes dried out.
The term Altiplano is also sometimes used to identify the altitude zone itself — and the type of climate that prevails within it, colder than that of the tierra fria but not as cold as that of the tierra helada; the latter is usually reckoned as commencing at an elevation of approximately 4,500 meters (or about 15,000 feet). Alternate names used in place of altiplano in this context include puna and páramos.
Information based on http://en.wikipedia.org/wiki/Altiplano