The Royal Gorge Route!
While not as lofty as the road Royal Gorge Bridge, the "hanging bridge" of the RR is perhaps more unique from an engineering perspective. When the Santa Fe built the line through here in 1879, they found the gorge too narrow at this point for a ledge. The solution was to suspend the RR from an A frame bridge at the narrowest point. Of course the Rio Grande is more famous for operating this route. As the result of a power struggle (the "Royal Gorge Wars"), the D&RGW was granted rights to this route in the 1880 treaty of Boston while ceding its own right to continue construction southward across NM. The other structure is the base station for an incline railway build up the side of the gorge as part of the tourist attraction at the top. This has been out of service since damaged by a wildfire that almost decimated the park in 2013.