Beyond Susques the road enters one of the emptiest and highest stretches of the whole journey, the high Puna, where the plateau runs on at around four thousand metres and the horizon is a rim of volcanoes. The road climbs gently towards the Paso de Jama, which is at about 4,200 metres and is the main Argentine border crossing into the Atacama.
The landscape is stark and unforgettable. Salt flats, shallow lagoons dyed pink by algae and flamingos, and bare mountains in shades of brown, red and grey lie in all directions. Vicunas graze on the sparse grass, and sometimes a fox or a rhea darts across the road. The sky is a deep, dark blue and the sunlight is fierce, so protect your skin and eyes. At night, the stars are astonishing, but the temperature falls well below freezing.
Riding here is mostly straight, steady and fast, with long views and sparse traffic, mainly trucks heading to and from Chile. The surface is generally good but can be damaged by frost and flood. Altitude plays tricks on both bike and rider: fuel injection can be rich or lean, and breathing, concentration and reaction time all suffer. Ride within your limits, pause often, and drink water. Headaches and nausea are signs to descend.
Weather is a serious risk. Wind, snow and ice can appear at any time of year, and the road can be closed by storms, sometimes for days. Border hours also matter, and the crossing can be shut in poor weather, so check before you commit. The best time is the dry season from April to October, but the cold in winter is severe. If you plan to continue, remember that the border formalities are done at a complex before the pass, with customs, immigration and agricultural checks, so bring patience and all your documents.