Narrow-gauge railways in Italy
Most narrow-gauge railways in Italy were built with Italian metre gauge, which is actually 950 mm (3 ft 1+3⁄8 in) because historically the Italian track gauge was defined from the centres of the rail instead of the internationally accepted method of measuring the gauge from the inside edges of the rails. Several metre-gauge lines were built in northern Italy.
Source: Wikipedia — Narrow-gauge railways in Italy (CC BY-SA 4.0)