The Tren A Las Nubes Train, Salta Province, Argentina

Currently, the train leaves Salta station for the 15-hour, 434-kilometre (270 mi) round trip to the viaduct La Polvorilla, located 4,220 m (13,850 ft) above sea level. The curved viaduct is 224 m (735 ft) long and 70 m (230 ft) high. Once the train has left Salta, it firstly enters the Valle de Lerma, and then the Quebrada del Toro, before reaching the puna. It is known as the Train of the Clouds because clouds can often be seen around and under the bridges and slopes of the landscape through which the railway passes.
The 10-car train can carry 640 passengers at an average speed of 35 km/h (21.7 mph). The C-C diesel-electric EMD GT22CU locomotive with 2,475 hp (1,846 kW) has two triple-sets of powered axles for traction, weights of over 100 t (98 long tons; 110 short tons), and consumes around 6 L (1.6 US gal) of fuel for every 1 kilometre (0.62 mi). The train, which stops only at San Antonio de los Cobres station for tourists to get off, see the town and buy local handicrafts, has a restaurant, folkloric events, and onboard medical facilities.
An average of 30,000 tourists visit the train each year. It runs from April to November, when the rain season is over, departing from Salta every Thursday and Saturday at 07:05, and returning around midnight. The train services include dining car, medical practice, audio, video, and bilingual guides. During the summer, from December to March, the Tren al Sol (English: Train to the Sun) travels from Salta to the Diego de Almagro station, at an altitude of 3,500 metres (11,500 ft).