The Durango and Silverton Narrow Gauge Railway
These trains run between those two towns in Colorado, through wonderful scenery.
My picture shows 486, a K36 which dates from 1925, returning to Durango after a day trip up to Silverton which stands at over 9,000 ft (2850 m).
Whether you are a steam enthusiast of lover of mountain scenery (or both!) the journey is highly recommended.