The Diakopto–Kalavryta railway has many unique features. It is a narrow 750 mm (2 ft 5 1⁄2 in) gauge line that runs 22,5 km (14 mi) and climbs from sea level to 720 m (2,360 ft) with a maximum gradient of 17.5%. The steep grade forced the engineers of the Piraeus, Athens and Peloponnese Railways (SPAP) to add a rack rail in the middle of the tracks. The trains use cogwheels that mesh in the rack rail and allow them to navigate the mountainous terrain. The government of Charilaos Trikoupis decided to build the rack railway in 1889 as an experiment to determine whether it could be helpful in remote and alpine regions. A steam locomotive constructed for this line in the late 19th century (ΔΚ 8003) is preserved at the Diakopto railway station.