There is, the Koralpe massif. Previously to get to Klagenfurt from Graz you first had to go north through a somewhat tight valley for about 50km before the train would turn to the south-west towards Klagenfurt, again tough alpine valleys, and with a lot of stops inbetween. The new route goes south/south-west immediatley, is very straight compared to the old route, and has at most 3 stops.