from Germany: Munich-Kufstein (Süd)-Mittersill-Felbertauern-Lienz-Tassenbach-Untertilliach (if you come from direction Germany and exit the motorway in Kufstein Süd you need no motorway-vignette!)
from Vienna:
Südautobahn motorway to Spittal/Drau-Lienz-Tassenbach-Untertilliach
or Südautobahn motorway to Villach-Kötschach-Lesachtal-Untertilliach
from Innsbruck:
via Brenner-Pustertal-Tassenbach-Untertilliach
from Italy:
motorway to Brixen-Pustertal-Tassenbach-Untertilliach or
The nearest railway station is Tassenabch (15 km away), the nearest main station is Sillian (18 km away). From there you have access to the public transport system (bus) taking you to Untertilliach .
The Innsbruck, Salzburg and Klagenfurt airports are about 2 1/2 hours hours away by car. From there you have access to the train or you can take a taxi to Untertilliach.