The Koralm railway will be a 130-kilometre twin-track line, directly connecting the cities of Klagenfurt and Graz and reducing the time of travel from currently three hours to about one hour.
The core of this line is the 32.9 km long Koralm tunnel with two completely new Intercity railway stations at its portals.
Extensive route studies took place between the area south of Graz and the Lavant Valley in 1996, which then resulted in the eventually selected twin-track route. Until Werndorf it runs almost in parallel to the historical Southern Railway Line in the direction of Spielfeld. From there the new route continues in the direction of Deutschlandsberg in a tunnel through the Hengstberg and the Lassnitz Valley. The 33 km long Koralm tunnel begins east of Deutschlandsberg and ends in the Lavant Valley between St. Andrae and St. Paul. After crossing the Lavant Valley the route runs in a tunnel into the Granitz Valley and continues under the Langenberg into the Drau Valley to the Village of Aich. In another curve, the route continues to Mittlern where it enters the existing railway line in the direction of Klagenfurt. Starting from Althofen, a second track will be added to the railway line. This will create a flat railway connection between the Muerz Valley and the City of Villach at an approximate altitude of 400 m where trains may be operated at a speed of 200 km/h.