Since being inaugurated in the late 1940s, Argentina's famous Tren a las Nubes - or Train to the Clouds - has been regularly ranked among the world's top rail adventures. It's also been frequently out of action, hampered by everything from financial problems to a derailment, and it's impacted on the route.
The service is currently running as a bus-and-train combination journey (Tuesday, Thursday & Saturday), with only the most westerly section between San Antonio de los Cobres and the Polvorilla Viaduct covered by rail. This is likely to remain the case until around 2022, when the full line is due to reopen.
It remains, however, one of the simplest ways of witnessing the country's towering north-west. Buses connecting with the train depart the attractive colonial city of Salta at 7am, though it's worth arriving here a day early to explore. Wander the crumbling 17th-century buildings or visit the curious Museum of High Altitude Archeology, where you can see mummified remains found in an Inca burial site on nearby Mount Llullaillaco.
The bus makes multiple photo stops en route as it snakes west through the tobacco fields of the Lerma Valley, passing forests of red-blossoming ceibo (the national flower of Argentina). From there, it rises into the brightly coloured rocky ravines of the Quebrada del Toro, slowly twirling up into the high-altitude desert plains of La Puna and - five hours after leaving Salta - the old mining town of San Antonio de los Cobres. This is where you'll board the train and set out across the high plateau to reach the Polvorilla Viaduct, a structure that sits at an atmospherically thin 4,200m above sea level, seemingly on top of the world.
