In the far northwestern reaches of the country, Ruta 40 crosses the Puna de Atacama (or Jujeña). It is on this territory of high plateaux interspersed with rolling sierras that the famous Viaducto de La Polvorilla stands. It is the last stop on the Tren a las Nubes. This technical feat, accomplished between 1930 and 1932 is 70m high, 224m long and rests on six pillars. Drawn in a distinctively curved line, the structure stands 4 182m above sea level, the highest railway bridge in the world.