Due north of Humahuaca and the turn-off to tiny Iruya, the RN-9 begins its long, winding haul up into the remote altiplano of northern Jujuy, known as the Puna Jujeña; this is a fabulously wild highland area of salt flats, lagoons speckled pink with flamingoes and tiny hamlets built of mud-bricks around surprisingly big Quebrada-style chapels. Some 30km north of Humahuaca, the RN-9 enters the Cuesta de Azul Pampa, a dramatic mountain pass peaking at 3730m and offering unobstructed views across to the huge peaks to the east. Past the bottleneck of the Abra de Azul Pampa, where fords along the road sometimes freeze, causing extra hazards, the road winds along to the bleak little mining town of Tres Cruces, where there’s a major gendarmería post – personal and vehicle papers are usually checked. Nearby, but out of sight, are some of the continent’s biggest deposits of lead and zinc, along with silver mines, while overlooking the village is one of the strangest rock formations in the region, the so-called Espinazo del Diablo, or “Devil’s Backbone”, a series of intriguingly beautiful stone burrows, clearly the result of violent tectonic activity millions of years ago, ridged like giant vertebrae. This road continues all the way to the Bolivian border at La Quiaca – an ideal base for visiting the remote corners of the province, such as Yavi, and its superb colonial church, and Laguna de los Pozuelos, with its sizeable wildfowl colony.