The Nariz del Diablo — Devil's Nose — is a sheer rock face in the Andes south of Riobamba where engineers in the early 1900s faced an apparently insoluble problem: how to descend a near-vertical mountain wall with a railway. Their solution was a system of switchbacks in which the train goes forward to one zigzag, reverses to the next, and so on down the slope — a breathtaking sequence that takes the track from the high Andean plateau down into the subtropical Chanchan River valley. The descent covers around 500 metres of altitude in just a few kilometres of track.
The journey starts from Alausí, a small town about 1.5 hours south of Riobamba by bus. Ecuador Railways has run tourist excursions along this section for years; check current schedules locally as services have varied. The ride itself — through cloud, past waterfalls, with views back up the cliff face — is one of the great rail experiences of South America. Book ahead at weekends.
Alausí is worth a quick look in itself: a pretty colonial town built on a series of ridges, with a large statue of San Pedro overlooking it from a hilltop. Even if you take the train only part of the way and return, the crossing of the Nariz del Diablo section justifies the trip.