The railway from Belgrade to Sarajevo was 444 km long, and, unusually for Europe, was built to a narrow gauge of 760 mm. The line was begun before the First World War and the last section was completed in 1928. The most difficult section of 57 km between Uzice and Vardiste across the Sargan Mountain, was begun in 1921 and opened in 1925. The section through the mountain range is 15.4 km long, but the distance as the crow flies between the stations at either end is no more than 3.5 km. The system of loops and hairpin bends is known as the ‘Sargan Eight’. The average gradient is 1 in 55, and the line goes through 22 tunnels; the longest, at the summit, is 1666 m long.
After a working life of less than half a century the line was closed in 1974, but the section between the station at Mokra Gora and the summit at Sargan Vitasi has been restored to working order, and trains for tourists are operated by two class 83 0-8-0 tender engines and two 0-6-0T tank engines. There are plans to extend the system to Visegrad. At Mokra Gora is another small preserved railway, a 600 m section of a 600 mm gauge forest line.