If you don't have a lot of time but you want to get to the mountains, you can take the number 25 bus to Untersberg mountain (it goes in the opposite direction to the number 25 to the airport). The bus journey lasts only 20 minutes and the bus terminates at at cable car at the foot of the mountain. It costs 18 euros for a return trip in the cable car, which takes another 15 or 20 minutes each way. It is the highest mountain in the area and the views are magnificent. You can go for a walk, ski, or just go to the quaint Alpine lodge, which is just outside the cable car terminus at the top pf the mountain, for some "gluwine", sausage or beer. This daytrip could be the highlight of your trip - it is beautiful!