I'd had the Abra del Acay on the para-hacer list for a while. It's the highest road in Argentina and gets up to about the height of Mont Blanc. It sounds a bit feeble to say we only went there in 2008 because we were still a little daunted by trying to go to Tajikistan, but that's more or less the truth.

We had a week or so riding north from Salta through the Querbrada de Humahuaca and over to Iruya, then back to the fleshpots of Salta before the assault on the big one. We rode to Campo Quijano and ate ice-cream; the next two days riding promised to be hard.

Hard indeed. The route towards San Antonio starts, along with the railway, by following a valley. Roads and railways like valleys and so do winds. Today’s wind was in the full and youthful vigour of Spring. Mostly it blew energetically against us; occasionally it hid in a side valley, where it would summon its full strength, and from where it would blast an ambush at us. Never mind, we were resigned to not going fast, the road being uphill ripio.

The mountainsides were arid, simply rock with cacti and scrubby clumps barely identifiable as vegetation, but where there was water in side valleys, there were oases of astonishingly lush willows and poplars. There are places named on the map, but they prove to be just names, perhaps one or two houses, but no shops. There was more of a village at Chorillos, and from here the road is paved – not that it made much difference to our speed, with this wind, and the mounting heat.

The valley opened out and as we came to midday we found perhaps the wind was beginning to turn, and slowly we approached Alfarcito, where there are smart new signs counting down the distances, with enticing promises of the delights to be found in Alfarcito, though we weren’t entirely sure if food was mentioned as such. I think, perhaps, there is some sort of religious institution here. We rounded the bend to find to find a small church and a couple of other buildings, and a non-operational comedor; lurking 500m further was a restaurant, this one rather more usefully supplied with food, rather nice food, in fact.

Santa Rosa wasn’t much further and there wasn’t much to this place either. In such a small place you would think that everyone would know everyone else, but nobody seemed to know who was supposed to provide any accommodation, which is especially puzzling as it happens to be the museum curator, and tourists are only going to stop here because of the museum. The curator and his wife are a friendly and very generous couple : they have a small dormitory for travellers, and they made us tea. Elsa said that Salta had had a lot of rain.

Too bad for Salta. We were up here, where the next day the sky was perfect unbroken blue and we only had 60km to cover. The gradient was gentle, in the broad valley, and the road was tarmac. The wind, however, was back, and as strong as ever. Now apart from a few patches of faint green by the river bed, there is nothing but rock. Even the cacti have given up. It is hugely empty: I find myself greeting a horse by the roadside – it will be road signs next.

The road climbs over a ridge to a large plateau below a summit and here the wind can have a free run directly at us. There was a sort of wave of tourist traffic on their way to a delicious lunch in San Antonio, something which we ourselves had long given up hope of. One bus advertised that it was supplied with oxygen, and we could feel smugly superior because we were cycling without the need for extra oxygen, but this hardly made anything to balance the fact that in an hour’s time the passengers would be enjoying tasty food and we would still be suffering this horrible road.

There is some relief from the wind when the road makes the final climb of the pass in zigzags. We see flocks of bright green birds, and flocks of yellow-and-black birds, which launch themselves in a burst of startling colour, like fireworks. While the climb up hides itself in zigzags there is no view, which builds the suspense for when you do reach the top. And here, we were looking over miles and miles of the puna, the high Andes, the roof of the continent : a huge open expanse, mountain ridges far around on the horizons, and far away, much further, snow peaks in another country.

We had a stretch of jubliantly fast descent before the gradient flattened out – and the unopposed wind blew more fiercely than ever, and the ripio recommenced. Our lunch-deprived legs struggled to find the fragments of surface that were less sandy or washboarded than the rest. But this was one of those rides where you know that however slow it is, you will get there eventually, and however awful it is, when you look back at the photographs, and remember the journey, you will have forgotten the sensation of pain and despair and tiredness and hunger, and you will remember only the adventure, and the achievement, and the grandeur of the miles of straight road traversing the land.

There was not very much to do in San Antonio which suited us perfectly, and we were especially thankful that there is a comfortable hotel with a menu worth spending four days to eat through.

We made a day ride to the Abra de Chorillos, the next pass on the way to Chile. The land was ever emptier than before. A strange mountain watched over us – dark minerals made it look as if it was under a permanent cloud, but the sky was still the same unmarked, untouched perfect blue – it was slightly unsettling, like something intangible wrong in paradise. But everything was perfect : from the pass, another marvellous and mysterious, unknown, deserted vista. For some reason the wind had gone elsewhere to torment some other victim, and had left us in peace to enjoy an idyllic picnic at 4400m.

Earlier in the trip we had entertained the idea of riding out the Salinas Grandes but I'm afraid it seemed a little too hard a ride for comfort and instead went by van. It's a trip worth making even if we did have to cheat. We had already seen faint sights of the Salinas from the passes and the hill above San Antonio – a shimmering white glow. The Salinas are marvellous – absolutely flat, and absolutely white, with the surface cracked into irregular tiles, and, in the low sun, with long distorted, otherworldly shadows.

And then, the big day. An early start, the sun was barely up, and it was cold, patches of ice in the river. 13km retracing our way back towards Salta, then the start of the Acay road. A long straight stretch of wide ripio, across a plain, towards the ridge of Nevado Acay, but we had no idea where the road might go after this – it turns out to bear right before veering back to make the climb. More than once we stalled in the sand, and the road took an age to get anywhere near the true climb, but there were llamas to look at.

Once we reached the hills the climb began with zigzags, ascending the slopes at first with views above a pale greenish valley, and vanishing into the thick of the slopes, as if trying to find a way through them for the first time; and because the lie of the land and the trace of route was a mystery to us, it felt that by moving into the land, we were creating it as we went forward. The valley below was unreal, magical, with delicate pale grass, and serene, with gentle vicunas and burros.

The numbers on our altimeters racked up satisfyingly; 4000m seemed commonplace now. After a steep section the road came out onto a corniche above the valley and climbed to 4400m. As we rounded a flank, we could see the ridge at the head of the valley, much much higher. And this ridge far above us really was where the pass was – we could see the glint of sun on a car coming down, and we could see the thin lines of the road. We had doubted that the pass height would be anything like the 4900m claimed, until now, when we saw it for real.

Three cars came down in the course of the climb, with cheers, and even photographs. We tried to make it look easy.

Towards the end we came out onto the ridge again, and to expansive views of a whole universe of puna. The last few zigzags looked exactly like the last bend on the Alpe d'Huez. But so do all climbs, and so do all dreams of climbs.

The summit of Nevado Acay crowned the pass – a dark and steep scallop. The height appeared to be barely 4800m, not quite that of Mont Blanc, but the air pressure was certainly an impressively low 555mbar. We ate some peaches and read a few lovely sentences of Proust's Nostalgia; we surveyed the road snaking down the gentle valley to the plain.

The other side was very different – a rugged, steep and narrower trench. The scenery is much more dramatic, with polychrome rocks, and outcrops, and cliffs, and the contrasting colours and different ridges were highlighted by the sunlight playing between the clouds, picking them out like a spotlight. The road dropped steeply at first, and lower down cut through sections of precipitous cliffs, where the valley was almost a gorge. The unexpectedness was truly exciting – it felt as though anything could happen in this landscape. Above the place called Negra Muerta, a huge dark valley led up into the clouds – what would it be like to climb it? Had anyone ever been there?

We were losing height fast, and soon reached the level of the stream, where springs have left weird mineral deposits on the rock faces; we passed the first farm, where Doñas Damiana and Flavia herd goats. The valley walls now became interesting red rock strata, and we began to see patches of grass, and trees, and farms, and fields, and hamlets, and schools, and tidy white churches, and people. Onwards down the valley, more mountains came into view and went; but we always had Ruta 40 leading us onward, telling us stories of its 5000km along the wild Cordillera, from high Bolivia, to Patagonia, to the end of the earth.

Routes do not become classics by being easy. We had left the pass at 3pm, and from there it was 45km to La Poma. There is an hosteria there, and we had reckoned we had more than enough time to reach it that day – it was, after all, downhill all the way. But we had lost most of the height in the first 15km, and from then on we had several fords, and that wretched headwind yet again, and about 100 short steep rises. It took us four hours.

The hosteria beat camping - they did us milanese, and suitably anaesthetic vino tinto. The champagne had to wait, but only until the next day.