The Yungas Road is a one-lane dirt track in Bolivia that drops 3,500 metres in 64 kilometres from the Andean passes above La Paz to the jungle town of Coroico, cut into cliffs without guardrails, once called the most dangerous road in the world, and now ridden down by mountain bike from ice to rainforest in a single morning. The road was carved into the mountainside in the 1930s by Paraguayan prisoners of war from the Chaco war, with hand tools and dynamite and almost no engineering, and for decades it was the only way from the capital to the Yungas valleys, a shelf three metres wide with drops of 600 metres off the edge, fog, waterfalls falling onto the road and trucks passing on the blind bends; it earned its name in the 1990s, when it was estimated to kill two or three hundred people a year, and it is the only road in Bolivia where traffic keeps left, so that the descending driver on the outer, cliff-edge side can see his wheels. A new paved road opened in 2006 and took the trucks away, leaving the old one to the bikes.
The rides start at the La Cumbre pass at about 4,650 metres, where the air is thin and the altiplano is bare and grey with snow on the peaks, and the first stretch is asphalt through the high valleys; then the dirt begins, and the bike drops through cloud into warmer air, the vegetation thickening from tussock to bamboo to jungle, past the crosses that mark where vehicles went over, under waterfalls that spray the track, with the drop always on the left. Riders stop at the hairpin named the Corner of Death, the sharpest bend on the descent, and walk to where the dirt simply ends in air. The morning ends in Coroico, at 1,200 metres, in heat and greenery, with the mountain gone into cloud behind. The Yungas Road is a road that time replaced, and the bikes now have it to themselves.