Reaching the clouds is the challenge taken up by the Tren a las Nubes. The train takes you up to a vertiginous 4 200m altitude (not for the fainthearted!), via numerous feats of engineering, including its terminus, the famous Polvorilla viaduct. The train itself (no doubt to compensate for the challenges of the trip!) is very comfortable and is equipped with a restaurant and a first-aid post for anyone suffering from altitude sickness.