Argentines fondly refer to RN-40, or Ruta 40, the country's longest road, as La Cuarenta (The Forty). Stretching from Cabo Vírgenes, the southernmost point of the Argentine mainland, to northernmost Ciénaga, on the Bolivian border, it's more than just a highway. Like Route 66 in the US, the road has its own ethos - inspiring songs, books and arguments - and is as central to a visit to Argentina as a football match or a milonga.

La Cuarenta runs a staggering 5224km - roughly the distance from Amsterdam to Kabul. Partly to make it more attractive for tourists, the road's route has been changed over the years. Ruta 40 now starts at the ocean at Cabo Vírgenes and winds north through eleven provinces, past twenty national parks and across 24 major rivers, before reaching the altiplano. There it breaks a record: the dizzying Abra de Acay, at 5061m, is the highest point on a national road anywhere in the world. Although sections are relatively busy, notably around Bariloche and between Mendoza and San Juan, most of La Cuarenta runs through Argentina's magnificent open spaces, seldom more than 100km from the majestic peaks of the Andes. Many visitors are drawn by the road's rugged mystique - a result of its inaccessibility and frequently poor condition - while others are put off for the same reason. The Argentine government has pledged to pave the entire road but hasn't completed the task yet.