Narrow Gauge Railroads. About seven such railroads still operate in North Wales. The railway shown here was built in 1902 to serve the lead mines, timber, and passenger traffic of the Rheidol Valley.  The steep terrain required many sharp curves and steep gradients; to reduce the cost of construction, a narrower track gauge (1' 113/4") was used. Today, these railroads carry vacationers. Click on a picture to see a larger view.