Assuming everything goes to plan – and that's a big assumption in these parts – tomorrow El Tren a las Nubes, the Train to the Clouds, will once again begin its clamber from the lovely colonial city of Salta into the mountains that divide northern Argentina from Chile. The train's operators are taking things easy to start with: just one round trip a week until the end of June, at which point it's due to become more frequent.
The tentative nature of the timetable is only to be expected: guidebooks cite the Train to the Clouds as one of the finest adventures available in the region, but even the most recent editions carry a footnote warning that the train has been out of action for several years and that it might be back on track in 2007... or maybe 2008. South American scheduling can be pretty relaxed.
In fact, the train did return late last year – albeit only for a couple of months – and I seized my chance to make the journey across the Andes from Argentina. The day I boarded was only its second outing since 2005, and there were clearly still a few teething problems to be ironed out. (The lighting failed on the journey back, which made for some interesting trips to the loo.) However, the refurbished carriages were smartly decked out, with multi-lingual guides presiding over each one, cleaners scurrying about throughout the day, plenty of legroom and breakfast and lunch provided.
But before this great train ride, I embarked on a splendid road trip. The adventure began in Poncho Huasi, a posada (bed and breakfast) set in a colonial house in the village of Cerrillos on the outskirts of Salta. It's run by Nick Evans, a rangy Englishman, along with his tiny Argentine wife, Alicia; it turned out to be the perfect base from which to explore the region.
Alicia has lived in the area all her life (her ancestors were among the gaucho leaders who helped oust the Spanish conquistadores in the 19th century), and the couple's enthusiasm for the area, combined with the local knowledge of generations, make them ideal guides. If they aren't free themselves to head off into the mountains or across the puna (grassland), they have a network of local contacts who are equally knowledgeable. It's a philosophy that strikes a neat balance between the straitjacket of a fixed itinerary and the vagaries of do-it-yourself backpacking, all on a very reasonable budget.
My plans had included a few tastings in the wine-producing region of Cafayate, where the vineyards are the highest in the world, but I spent more time in Salta itself than planned: it is quite rightly known as la Linda, the beautiful. And once we hit the road north, with Nick at the wheel, I was too diverted by the red-and-yellow mountains and deep gorges to bother with bodegas, so I left the vineyards for another time. We paused in the pretty town of Cachi, where Alicia spent her holidays as a child. We ate ice-cream in the square and strolled down sunny, cobbled streets. We wandered down the Devil's Throat, and were serenaded on pan pipes by a busker who had set up his pitch in a towering natural amphitheatre, two of the many startling rock formations on the road through the Canyon de las Conchas.
We then picnicked on llama salami and goats' cheese at Quilmes, the ruined foundations of a town that resisted both the incursions of the Incas and of the conquistadores. Climbing up into the hillside fortifications reveals the terraced layout of this ancient place, but the high mountains behind it couldn't protect it forever. The Spanish eventually lost patience with the stubborn inhabitants, the Diaguita Indians, in 1666 and force-marched them over 1,300km to Buenos Aires; most died on the way, and the survivors were enslaved.
A new historical chapter is being written here: the descendants of the Diaguita Indians are attempting to reclaim their former homeland and are currently engaged in a very modern legal stand-off with the owners of a rather splendid-looking hotel that has been built near the site, but is now surrounded by tape that bears the Spanish equivalent of "do not cross".
One of the greatest pleasures of the road trip was stopping off in places the guidebooks are likely to overlook. Villages such as San Carlos or Angastaco are mere specks on the map, but even the tiniest settlement here has a beautifully kept square and a café for coffee and an empanada or two. The cool, dimly lit churches built of adobe, with ceilings and doors of cardon (cactus wood) are filled with unexpected treasures. Some house life-size statues of the Virgin Mary, adorned with real hair, outfits that are changed according to the seasons, and skirts hung with silver offerings from the grateful, symbolising her successful intercessions: a heart, a child, a cow. A few hundred metres up the road there might be the scene of a Pachamama, with sacrifices of food to the spirit of the earth mother. There is equal devotion here to both Christianity and far earlier faiths.
These quiet hamlets are certainly one-horse towns, but you can't help but feel jealous of the horse. Nick pulled the car over in one such and we contemplated the pastel adobe houses, the wide horizons peppered with cacti, and the framework of the mountains. It was absolutely silent. "Cities are all very well," he said, "but this is what it's really all about, isn't it?"
The view in front of us, like so many around here, would be the perfect setting for a Western movie. It's hard not to feel the car is out of place here. We should have been galloping across the desert in the solid Argentinian-style saddle that makes horse riding so easy and comfortable, or gliding through the canyons and mountains by train, on tracks that are an enduring testament to the engineers of the last century.
The vertiginous railway line of the Train to the Clouds once ferried trucks of minerals from the rich mines of northern Argentina towards Chile. It's often described as the "most amazing train in the world".
The statistics reveal why: work on the track began in 1921 and took 27 years to complete because of the extraordinarily demanding terrain, and the 217km, 16-hour round trip from Salta to La Polvorilla viaduct u
oincludes 29 bridges, 21 tunnels, 13 viaducts, two spirals and two zigzags. La Polvorilla, a feat of engineering comparable to that of the track itself, is the highest viaduct in the world, at over 4,200m (the summit of the Matterhorn is barely higher). This magnificent conduit is an elegant structure and, from a distance, its steel struts look as fine and delicate as a spider's web, slung over a deep gorge.
More unusual facilities on board El Tren a las Nubes include oxygen cylinders and medical staff. This seemed a bit over-cautious in Salta, at a mere 1,187m, but by the time we reached the highest point, the nurses were dealing with a steady stream of white-faced, grimacing altitude-sickness sufferers.
I escaped with only a mild headache, owing to a supply of the local remedy for high places: coca leaves, which have been used against the effects of altitude for centuries in South America. The plant constitutes the raw ingredient of cocaine, but the simple dried leaves are perfectly legal. Most of the locals on the train were quietly chewing a handful, and I did the same; the taste is bitter, and the chemicals the leaves contain numbs your mouth like a dentist's injection, but the habit also staves off the faintness that affects some people in the mountains.
The train climbs through scenery that is as austere as it is beautiful. Once Salta is left behind, the high-altitude stations stand, somewhat forlornly, in the middle of nowhere, some with not even a road in sight. At Diego de Almagro halt (3,305m above sea level), a pump bearing the maker's stamp of H Pooley & Son of Liverpool still stands in the abandoned station building. The makers will be heartened to learn that its green paint shows not a trace of rust.
The bills of lading and tickets from decades gone by flapped in the stiff breeze that blew in through the broken windows, handwritten in immaculate copperplate; other passengers picked them up as souvenirs and I wish I'd slipped one into my pocket to decipher later.
At San Antonio de los Cobres (3,774m), the only town along the route, the low-built houses and tiny market are dwarfed in the vast emptiness, scoured by the dusty mountain wind. Most of us who stepped out of the train here only stood for a moment, contemplating the bleakness, before returning to the shelter of the carriage; this isn't a place where you would want to live.
San Antonio is the last place the train stops before La Polvorilla itself. It glides across the viaduct before reversing back, poised for the return journey. The trip back to Salta is completed in the dark; you arrive back at the station 15 hours after leaving early in the morning. As days out go, it's surprisingly tiring. But the truly dedicated can forge on to Chile by cargo train, a rather less luxurious mode of transport than El Tren a las Nubes. Socompa, on the Chilean border, is a further two days away from La Polvorilla; on the other side of the viaduct, the tracks continue, winding onwards through the mountains
The writer flew to Buenos Aires via Madrid with Iberia (0870 609 0500; iberia.com) with onward connections to Salta with Aerolineas Argentinas (0800 096 9747; aerolineasargentinas.com ). A specialist such as Journey Latin America (020-8747 3108; journeylatinamerica.co.uk ) offers through fares from £735.
To reduce the impact on the environment, you can buy an "offset" through Abta's Reduce my Footprint initiative (020-3117 0500; www.reducemyfootprint.travel ).
Tren a las Nubes (00 54 11 5246 6666; trenalasnubes.com.ar ). One-day round trips cost $120 (£86), including breakfast and an afternoon snack.
Posada Poncho Huasi, Guemes 760, Cerillos, Salta (00 54 387 4999 035; ponchohuasi.com ). Doubles from £24, including breakfast.
Argentina Tourist Board: turismo.gov.ar
Five scenic rail routes through Latin America
Over the Andes from Lima to Huancayo, Peru
This line had the distinction of being the world's highest passenger railway, reaching 4,781m at Galera – until 2006, when the railway to the Tibetan capital, Lhasa, opened. A recently introduced open-sided observation car allows passengers to appreciate the staggering mountain landscapes, dizzying drops from viaducts and the zig-zags by which train gains height. Careful planning is needed, as the train usually operates on only two days a month.
Where: The 18-day Peruvian Trail from 6 October includes this and the journey on to Huancavelica, organised by Ffestiniog Travel (01766 772030; festtravel.co.uk )
How much: £3,700
How long: 12 hours; 332km
The Great Brazil Express
This sumptuously refurbished 44-seat train offers a way of exploring the country on three- to 10-day itineraries, all starting from the south-eastern town of Curitiba and using small, independent luxury hotels along the route. Though the train has a bar and serves light refreshments, meals are taken in restaurants. Destinations include such "must see" sites as Iguacu Falls and the Pantanal.
Where: Great Brazil Express (0800 141 2143; greatbrazilexpress.com )
How much: From €€1,177
How long: 3-10 days
The Old Patagonia Express, Argentina
Ramshackle though this railway through the bleak mountains of southern Argentina may be, it is full of character. When Paul Theroux came this way and took the train's sarcastic name for his second book of railway travels, you could travel between Ingeniero Jacobacci and Esquel in about 23 hours, derailments permitting. Today only the section between Esquel and Nahuel Pan sees regular trains, but the full line has reopened for charter trains.
Where: The 17-day Old Patagonia Express tour from 14 November covers the full line and is operated by the Railway Touring Company (01553 661500; railwaytouring.co.uk )
How much: £4,795
How long: 402km
Mexico's 'Grand Canyon'
Two trains a day travel each way between Chihuahua and the Pacific coast at Los Mochis, reaching a 2,460m summit before dropping down to sea level over a line that was completed as recently as 1961. The scenery varies from prairie to deep river valleys, but the highlight is the Copper Canyon. The train stops at Divisadero station to allow passengers to walk to a viewing platform and gaze 1,000m down into the chasm.
Where: Explore (0844 499 0901; explore.co.uk ) offers 13-day Copper Canyon & Tequila Express tours
How much: £2,595–2,895 depending on departure date
How long: 15 hours/655km
Cuzco (Poroy)-Machu Picchu, Peru
PeruRail's luxury Hiram Bingham is a full-day visit to the Inca site of Machu Picchu, with meals, drinks, transfers, admission and return to Cuzco included in the price. The Vistadome is rail journey only but offers snacks on board. The scenic journey, which passes near the Inca ruins of Ollantaytambo and takes in the Sacred Valley, used to begin with a series of spectacular zig-zags out of Cuzco but this has been abandoned, necessitating a 20-minute taxi ride to join the train at Poroy.
Where: PeruRail (00 51 84 581414; perurail.com )
How much: Hiram Bingham US$588, Vistadome US$71 one way
How long: Hiram Bingham 12 hours (including stops), Vistadome 3 hours; 107km