Salar de Atacama is the largest salt flat in Chile. It is located 55 km (34 mi) south of San Pedro de Atacama, is surrounded by mountains and has no drainage outlets. To the east is enclosed by the main chain of the Andes, while to the west lies a secondary mountain range of the Andes called Cordillera de Domeyko. Large volcanoes dominate the landscape, including the Licancabur, Acamarachi, Aguas Calientes and the Láscar. The latter is one of the most active volcanoes in Chile. All of them are located along the eastern side of the Salar de Atacama, forming a generally north-south trending line of volcanoes that separate it from smaller endorheic basins.
The salt flat encompasses 3,000 km² (1,864.11 mi²), is about 100 km (62.14 mi) long and 80 km (49.71 mi) wide, which makes it Americas' second largest and is also the second in the world, after Salar de Uyuni in Bolivia (10,582 km²). Its average elevation is about 2,300 m asl. The topography of the core portion of the salar exhibits a high level of roughness, which is due to that the surface of this area is permanently free of water, unlike the most of the other salt flats, as for example the Salar de Uyuni, which is periodically covered with shallow water. Some areas of the salt flat form part of Los Flamencos National Reserve. The Lagunas Cejar is a sink hole lake in the Salar de Atacama, 18 km from San Pedro, Chile. It has a 40% concentration of salt, producing an effect of floating like the Dead Sea.