One of the most spectacular train journeys in South America is the 'Train to the Clouds' in Argentina. Starting low in Salta, at an altitude of 1187m above sea level, the 217km journey rises to a maximum height of 4200m above sea level.
The route includes a huge number of spirals, switchbacks and zig zags owing to the height difference along the route. By including these design elements, the route avoids the need for cogs or other measures for steep slopes.
On-board, the train offers meals and translator services, as well as a doctor on-hand to deal with any altitude related illnesses. The return trip lasts around 16 hours, although passengers can choose to leave the train at San Antonio de los Cobres on the return journey in order to take in some of the other sites in the vicinity, such as the salt flats (a taxi ride away).
The train fare includes breakfast and an afternoon snack, and a full bar and restaurant service is available. The food is quite good, albeit expensive. You may wish to buy lunch in Salta before boarding the train, and pay for dinner on-board the train in the evening.
Travel Tip: sit on the left hand side of the train when you board in Salta. At the summit, the train reverses, so you will have the same view on both the outbound and return journeys, but the left hand side is generally the better view.