A narrow gauge railway is a type of railway with a track gauge that is narrower than the standard gauge of 1,435 mm (4 ft 8.5 in). Common gauges include 1,000 mm (3 ft 3 3/8 in) and 762 mm (2 ft 6 in). These railways are often used in mountainous or rugged terrain where building standard gauge tracks would be more difficult and expensive. Narrow gauge railways are popular for tourist attractions and heritage lines, as they provide a unique travel experience. They are also used in industrial applications, such as logging and mining, where the lower construction costs and tighter curves are advantageous. Examples include the Darjeeling Himalayan Railway and the Wiscasset, Waterville and Farmington Railway.