At 6,288 feet (1,917m), Mount Washington is New Hampshire's highest peak, dominating a verdant valley that bursts with colour in every season. However, if you're not keen on a hike, you're in luck. The mountain is home to the world’s first mountain-climbing cog railway, in operation since 1869. Brightly coloured trains chug along the 3.5-mile (5.6km) track, at a 37% gradient at certain points. At the summit, you'll have an hour to take in the views that on a clear day include five states, Canada and the Atlantic.