About this journey

San Antonio de los Cobres station sits on the Puna de Atacama plateau, the starting point of the 44 km metre-gauge climb along the Ferrocarril Antofagasta-Salta toward Viaducto La Polvorilla. Construction of the line officially began in 1921, designed by American engineer Richard Maury, who chose an entirely rack-free approach to conquer the altitude — a decision that demanded 29 bridges, 21 tunnels, 13 viaducts, 2 spirals, and 2 zigzags along the full route. The zigzags allow the train to gain elevation by reversing back and forth across the mountain slope rather than relying on toothed traction.

The line earned the popular name Tren a las Nubes in the early 1960s, when vapour from the then-steam locomotives formed large plumes in the cold Andean air. The 1,000 mm gauge track carries predominantly freight — lithium carbonate, borax, and brine from the mineral-rich Atacama region — with passenger services running only this upper segment between San Antonio de los Cobres and La Polvorilla. The journey ends at the curved La Polvorilla viaduct, completed on 7 November 1932: 224 m long, 64 m high, and standing at 4,220 m above sea level, the highest point of the entire line.