You cross Abra Málaga in one climate and descend in another. On the Urubamba side the valley is dry, dusty and Andean, with terraces, eucalyptus and the white shoulders of Nevado Verónica high above. Then the road tops out at 4,316 metres, a cold, windswept saddle of grass and rock, and plunges into the cloud forest on the eastern slope, where the air gets thick, wet and green and the temperature climbs a degree with every switchback. By the time you reach Santa María, a thousand-odd metres lower, you are in the edge of the Amazon basin, with orchids, bamboo, coffee bushes and mist hanging on every ridge.
The riding is wonderful and slightly nerve-wracking. The climb from Ollantaytambo is a steady series of hairpins on tarmac, with fast, open sections between them, and the descent on the far side narrows, drops and twists through damp forest. Fog is the usual condition at the top, and the road is often slick and strewn with small landslides and fallen branches, so ride within what you can see. Mornings are the clearest, while afternoon cloud rolls in fast and can bring rain, hail or even a dusting of snow. Wear warm gear at the top, and carry rain gear for the bottom.
The pass is part of an old route that connected the highlands with the coffee and coca lands of the jungle valleys, and in Inca times it carried travellers to the lowlands, though the modern road is much newer. Beyond Santa María, a gravel road continues to Santa Teresa, the usual jumping-off point for the hydroelectric station and the rail line to Machu Picchu, and it is a rougher ride that demands care.
Nothing stands at the top except wind, a few roadside shrines, and a view that is yours if the cloud lifts. Fill the tank in Urubamba or Ollantaytambo, about fifteen kilometres away on the Cusco side, and bring food and a thermos. If the weather turns bad, do not hesitate to turn back, because the road is not a place to be caught after dark. The descent into the green valley, with its warm, wet air and the smell of woodsmoke and earth, is one of the most dramatic changes of scene you can have on two wheels.