Narrow-gauge railways in Norway
In Norway, a number of main lines were in the 19th century built with narrow gauge, 3 ft 6 in (1,067 mm), to save cost in a sparsely populated mountainous country. This included Norway's first own long-distance line, the Røros Line, connecting Oslo and Trondheim, 1877.
Source: Wikipedia — Narrow-gauge railways in Norway (CC BY-SA 4.0)