Werfen

Werfen needs 1 day: the Eisriesenwelt ice caves -the largest ice cave in the world open to the public, with 42 km of galleries- on one end, and Hohenwerfen Castle, on a crag overlooking the Salzach Valley, on the other. May-September is the only season the ice caves are open. It's expensive, with the cave-and-cable-car combo among the priciest outings in Austria. The castle was a filming location for scenes in «The Sound of Music» and hosts live birds-of-prey shows, and the caves -formed over 100,000 years ago- hold eternal ice even in the height of summer.