The Georgetown Loop is a narrow gauge (3') railroad that connected the mining towns of Georgetown and Silver Plume. The track was designed as a corkscrew and includes horseshoe curves and four bridges across Clear Creek. It was completed in 1884 and operated by the Colorado & Southern Railway for both passengers and freight from 1899 - 1938. The loop was rebuilt in the 1970s. 

Here is a link to the photos I took, the last four are in the town of Georgetown.