Before leaving Tupiza we visited some of the tour agencies which run 4x4 excursions into these high mountains. We needed basic information like critical junctions and availability of food and water.

We set off into a blazing hot Tupiza sun and were soon wishing for higher elevations if only to cool things off. We figured that if we had to climb all day, that'd be fine. That's what we do.

We had picked a good spot to camp. It was sheltered from the wind and we had a tranquil night and sunny morning. When I rolled up my tent I found a surprise underneath: a small scorpion.

In La Quiaca, Argentina, we had shared a room with two English travellers who had done a 4x4 excursion from Tupiza to the lagoons -- and so had been on this route. We'd plied them for information about it, and what we came away with, aside from memories of their bewilderment that anyone would cycle this route, was that there is a "high" road in addition to the main route. Their driver had taken them out on the low road and back on the high one.

"It's high but the road quality is better. The lower one follows a river and is quite rocky," the guy had said. "The high road is also much more scenic. There's nothing up there, so you'd need to be prepared and have enough of your own food and water."

We woke up to a bright day and hot breakfast. One of our fellow breakfasters, "Nain" was very curious about us. He looked as tired as we did. A bit homesick. No wonder – his wife and children live in Cochabamba; he visits them once a month.

"Yo tambien voy por estos lados," he said. "En moto."

A late start today because we indulged in multiple breakfasts and cups of tea on top of coffee. It's always that way up here. Someone will bring you out the necessaries for coffee and tea. These are such luxuries and the caffeine is such a pleasure, we just drink everything they bring out. Yes, we know this is self-defeating: caffeine is a diuretic.

The river ensured us a cold start. We cursed the water as we pulled our kit together and packed up for the road; the joints are unwilling and the heart starts slowly in cold conditions.

Last night a burro stood a hundred feet away from us making a terrible racket. After our Salinas Grandes burro encounter back in Argentina, we are in no mood to put up with burro shenanigans. It is true that he was here first, and that we are interlopers. But we are the dominant species.

We had llama again for breakfast and then set out. We overtook the misleadingly named Quetena Grande within five kilometres and thereafter embarked on another long, loney strectch of high-altitude desert.

As we pulled our tents together and packed up camp, we spied a small object on the far side of the laguna slowly making its way round the periphery. Eventually it became clear that this was a cyclist. We cooled our heels and awaited his approach.

The temperature was -13 inside the tent last night. Yet, for the first time in a while, I've slept the whole night through.

We pack up amid bright sunlight, giddy at the day's prospects. We will cycle down to Laguna Verde, at the foot of Volcan Licancabur, and from there, up and over the pass into Chile.