Located on the northern Peloponnese, it runs 22 kilometres (14 mi) from Diakopto through the Vouraikos Gorge and the old Mega Spilaion Monastery and up to Kalavryta, stopping en route at Zachlorou.

[4] At the Diakopto terminus, the line connects with the new standard-gauge Athens Airport–Patras railway; as of 2019[update] the new track is in place in a cutting through the station yard.

In the middle of the route, after 12.6 kilometres (7.8 mi), it makes a stop in the village of Kato Zachlorou, while at this point it serves the visitors of the historic Monastery of the Great Cave.

[8] The line was built by French company ATON,[9] with the assistance of Italian craftsmen who had acquired great experience in similar projects in the Alps.

[8] It was one of the most difficult projects for its time due to the very inaccessible terrain but also the high altitude at which it ended, as the Odontotos is the steepest railway in Greece.

The railway includes three stretches of rack: where the gradient exceeds 10%, gear wheels on the train engage with toothed rails in the centre of the track.

During the Axis occupation of Greece (1941–44), Athens was controlled by German military forces, and the line used for the transport of troops and weapons.

Freight traffic declined sharply when the state-imposed monopoly of OSE for the transport of agricultural products and fertilisers ended in the early 1990s.

[citation needed] Between 2007 and 2009 OSE undertook large scale improvement works and upgrades across the line, including bridges, enlargement of tunnels and replacement of the rack and testing of new rolling stock.

Passengers buying a round-trip ticket from Diakopto and taking the first train to Kalavrita were allowed to return later in the day on any of the other service.

In addition, a steam locomotive (ΔΚ 8003, delivered by Cail in 1891) is preserved at Kalavryta station and has been used occasionally for special trains.

[24] The railway and its Diakofto steam engine (called Madame Hortense) feature prominently in Gerald Durrells 1974 fantasy children's book "The Talking Parcel and its film adaptation".