The "Tren a las Nubes" is one of the most famous trains in South America. The tourist train uses a part of the Trans-Andean Railroad from Salta, Argentina, to Antofagasta, Chile. At the moment, however, the train runs on the last 21 km of line only, from San Antonio de los Cobres to the Polvorilla Viaduct. The train reaches an altitude of 4220 m above sea level at its highest point at the Polvorilla Viaduct.