Tehachapi Loop

Considered one of the railroad engineering wonders of the world, the Tehachapi Loop is a spiral of railroad track 0.73 miles long which passes over itself courtesy of a tunnel/bridge combination. The Loop allows trains to ascend "The Tehachapi", the mountain pass at the southern end of the Sierra Nevada Mountains, on an easy grade.

View of the Tehachapi Pass including Walong looking west toward the San Joaquin Valley. Some controversy exists over the naming of the Walong, the area inside the loop. Older sources indicate that it is a bastardization of some dialect of Chinese, with a meaning related to "dragon" - a name given to it by the Chinese workers who built the Loop. Wikipedia cites a different origin, specifically that it was named after Southern Pacific District Roadmaster W.A. Long. I rather prefer the first explanation...

A westbound freight train descends the pass, approaching the Loop.

The freight train passes beneath itself on the Loop.

The tail of the train passes over the body moving through the tunnel.