From the south of La Paz to the borders of Chile and Argentina, this limitless immensity invades its visitor to an overwhelming sense of loneliness. The barren mountains seem suspended in an unreal world. Most of the Altiplano was once covered with the prehistoric lakes Mirichi and Tauca. They have disappeared here about 10 000 years, leaving a desolate landscape, composed of arid pampas, deserts of salt and brackish water areas.