West of Denver on the former Denver and Rio Grande Western - now UP's Moffat Tunnel Sub - you'll find the awesome engineering of Little Ten and Big Ten Curves.
The original architects of the railroad needed a way for the railroad to gain a lot of elevation over a short distance without exceeding a 2% grade. The solution was a series of 10° curves that wind around and take the tracks virtually all compass directions. Great for pictures as you can almost always find an angle with good lighting!
Here, we see BNSF's Provo-Denver coming out of Eisele (formerly Clay) at the west end of Big Ten Curve, making its way around and down. In the siding at Rocky below, the Provo-Denver's counterpart, the Denver-Provo, is patiently waiting for its turn to continue west.
