Davos, Switzerland to Tirano, Italy

At around 20mph, the Bernina Express must be one of the slowest trains to earn that description. You wouldn’t want it to go any faster though, since it rears and plunges over the southern Alps, navigating 196 bridges, some of them spanning dizzying chasms, and boring through mountains via 55 ­tunnels. The views from the glass-roofed panorama car as it climbs 2,253m over the Albula pass to St Moritz are staggering. And the engineering skills that zigzagged the track over precipitate terrain are so impressive that it has ­become a Unesco World Heritage Site. Journey time: four hours, from £35 one way plus reservation fee, rhb.ch