Rennweg is located in the Katsch Valley (Katschtal) between the Hohe Tauern range in the west and the Gurktal Alps (Nock Mountains) in the east, along the upper part of the Lieser River, a left tributary of the Drava.

In the north runs the main chain of the Alps, with the Katschberg Pass mountain area considered one of the largest skiing resorts in Carinthia, bringing much of Rennweg's reputation.

The settlement arose in the valley north of Rauchenkatsch Castle in the Duchy of Carinthia, first mentioned as castrum chaetze in an 1197 deed.

The area, which initially was ceded to the Bishops of Freising by King Henry II of Germany in 1007, was then held by the Archbishops of Salzburg.

The resort's longest run is six kilometres, leading from the top of Aineck mountain to the village of Sankt Margarethen.