6. Durango & Silverton Narrow Gauge Railroad
Durango, CO – Silverton, CO
On the Durango & Silverton, the man-made sights are just as compelling as the natural ones. It's one of the few lines in the U.S. that still operates steam locomotives, and many of the route's passenger coaches are more than a century old. Trips depart from Durango Depot, built in 1882 and preserved in its historical form. (If you can't get enough of historic steam trains, plan to visit the nearby Cumbres & Toltec Scenic Railway, too.)
The scenery is no slouch, either. The route closely follows the Animas River through the Rockies, with beautiful views of foliage, peaks, and canyons. A highlight is the Highline, a stretch of track where the train slowly edges along a narrow cliff. The route continues running in winter with a slightly shorter itinerary and a lot more snow.