Tren a las Nubes

Tourist train service in Argentina
the tourist passenger train service

| ridership =
| ridership2 =
| website =
| start = San Antonio de los Cobres
| stops = 20
| end = La Polvorilla Viaduct
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| journeytime = 8 hours (including rest stops)
| frequency = Four times a week the fifth highest railway in the world. Originally built for economic and social reasons, it is now primarily of interest to tourists as a heritage railway, though cheaper tickets are also available for locals to use the train as transport.

The railway line has 29 bridges, 21 tunnels, 13 viaducts, 2 spirals and 2 zigzags. Because of the design decision not to use a rack and pinion for traction, the route had to be designed to avoid steep grades. The zigzags allow the train to climb up driving back and forth parallel to the slope of the mountain. The train runs four days a week, departing from San Antonio de los Cobres (where passengers arrive from Salta by bus) to La Polvorilla viaduct. though most tourists simply do the 8 hour one way trip and return by other means. The train is composed of a dining carriage, bar carriage, a first aid area and two passenger carriages with room for 170 people, though this is expected to increase to 400 over time. Currently, the train leaves San Antonio station for the 13 hour, The curved viaduct is long and high. Once the train has left Salta, it first enters the Valle de Lerma, and then the Quebrada del Toro, before reaching the puna. There are numerous stops along the way, some with markets selling artisan goods and locals offering regional cuisine. The La Polvorilla viaduct, the highest of the line, was finished on 7 November 1932. The route was designed by American engineer Richard Maury, (who later died in Salta) and after whom one of the stations has been named. The complete railway was inaugurated on 20 February 1948, following numerous delays and complications and a two year period where work was stopped. The line got its name in the early 1960s after students filmed a trip on the Salta Antofagasta railway from inside the train carriages, often showing the vapor from the then steam locomotive which – together with the cold mountain air – formed large vapour plumes. The footage was later offered to the Clarín newspaper to make a documentary, which was subsequently called Tren a las Nubes ("Train to the Clouds") because of the vapour clouds in the film. Ferrocarriles Argentinos (FA) later adopted the name to make it more appealing to tourists. It was not until 1972 that the route began being officially used by tourists as a heritage railway.

In July 2014 a train derailed near Abra Muñano, at a height, before reaching San Antonio de los Cobres. About 400 passengers had to be evacuated from the train. After the incident, the Government of Salta led by Juan Manuel Urtubey rescinded the contract with "Ecotren", alleging safety failures. Following these events, the service was re nationalised and the Province took over the operation and maintenance of the service. through a recently created state owned company, "Sociedad del Estado Tren a las Nubes SFTSE". although the service did not begin running again until 4 April 2015. During the 8 month closure of the line, both the National Government and the government of Salta had restored much of the railway track as well as the rolling stock. For that refurbishing, coaches were remodeled by the Province along with freight transport company Belgrano Cargas, while diesel locomotives were repaired at Alta Córdoba workshops. As of August 2017, the majority (>80%) of the route is by bus.