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.
The Argentinian section of the railway is about 450 km long. It crosses the border to Chile at the Socompa Pass, at 3858 m above sea level. The Chilean part of the railroad is about 330 km long. The Argentine section's official name between Güemes, Salta, and Socompa is "Ramal C-14."
Eng. Ricardo Fontaine Maury projected and built the railroad from Salta over the Andes. Mauri avoided a rack system used in other Andean Railways and instead used switchbacks and spirals to help the railroad overcome the significant altitude difference. The railroad climbs from Salta at 1187 m to Abra Chorillos at 4475 m above sea level.
The section of line used by the "Tren a las Nubes" travels over 29 bridges and 13 viaducts, and crosses 21 tunnels. The train does two spirals and two switchbacks on its way to the Polvorilla Viaduct at 4220 m above sea level.
Regular passenger trains between Salta and Antofagasta existed until 1981. Later, a weekly freight train with passenger transport ran between Salta and Socompa. Today, "Ferrocarriles Argentinas" does not operate regular passenger trains between Salta and Socompa; however, cargo trains run sporadically between Argentina and Chile.
The nickname "Tren a las Nubes" translates into English as "Train to the Clouds." The name is due to a film made by two students from the National University of Tucumán during the 1960s. The students traveled the Salta-Socompa section aboard a regular steam-pulled passenger train and asked the engine-driver to release steam at the Polvorilla Viaduct. They planned to film the release of steam from the windows of their wagon. However, the low temperatures at the viaduct prevented the steam from dissipating, creating an illusion that the train was riding over the clouds.
The first "Tren a las Nubes" from Salta to the Polvorilla Viaduct ran on July 16, 1972. After that, state and private tour companies variously operated the train. In 2005, a defective locomotive left passengers stuck in freezing temperatures at high altitudes. This incident led to the withdrawal of the operating license from the government.
In 2008 Ecotren took over the operation of the "Tren a las Nubes," but in 2014, the operator had to evacuate 400 passengers from the "Tren a las Nubes" at 4000 m above sea level due to the poor maintenance of the railroad. As a result, the Province of Salta took over the operation of the tourist train. Currently, the train operates only on the last 21 km or rail between San Antonio de Los Cobres and the Polvorilla Viaduct. Since 2014, it has been impossible to travel on the "Tren a las Nubes" from Salta to San Antonio de Los Cobres.
Individual travelers can book a day tour from Salta. The train ticket includes the motor coach journey from Salta to San Antonio de los Cobres. It is also possible to buy a ticket only for the train part of the trip.
Passengers board the train at the railway station in San Antonio de Los Cobres. The train journey to the railway station of "Mina Concordia" takes about 45 Minutes. Located in the middle of nowhere, Mina Concordia is an abandoned silver mine with a small railway station where the locomotive is moved to the other end of the train. The engine then pushes the train for another few kilometers to the Polvorilla Viaduct.
The journey of 21 km from San Antonio to the Polvorilla Viaduct takes about one hour. Once there, the train crosses the viaduct in both directions in slow motion and then stops at one end, where locals have organized a small souvenir market on the platform for the benefit of train passengers. There is also a lookout next to the platform where travelers can discover excellent views of the viaduct and the train. After 30 minutes, the train returns to San Antonio de Los Cobres. The return journey takes about 40 minutes.
The train has a small dining car where snacks can be purchase. There is a nurse on board the train and oxygen available in each carriage. Bilingual tour guides explain the train journey, the railway, and the sites.
As soon as the train is back, travelers have time to get lunch in one of the local restaurants in San Antonio de los Cobres. The buses travel back to Salta after 3 p.m. in order to reach the city between 6 and 7 p.m.
It is a pity that the "Tren a las Nubes" doesn't run from Salta, as this railway journey is the most impressive between Puerto Tastil Km 101 and Diego de Almagro Km 131. This section of the railroad is extremely remote and not accessible by car. The highway only meets the railroad tracks again below the "Abra Blanca" Pass at 4080 m above sea level.
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