Werfen in the Salzach valley 45 minutes south of Salzburg by train is the base for two major attractions: the Eisriesenwelt, the world’s largest accessible ice cave with 42 kilometers of passages inside the Tennengebirge, and Burg Hohenwerfen, a well-preserved 11th-century archiepiscopal fortress above the valley. The ice cave is accessible May to October and requires warm clothing; book guided tours in advance for July and August. Burg Hohenwerfen is open year-round. Staying overnight in Werfen gives access to both sights without the time pressure of a day trip from Salzburg. Train from Salzburg takes 45 minutes; bus from the station to the ice cave base adds 15 minutes.
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Werfen
The Eisriesenwelt ice cave runs for 42 kilometers inside the Tennengebirge massif above Werfen, though only the first kilometer is accessible to visitors. That kilometer contains ice formations up to 20 meters high and chambers large enough to hold the Vienna State Opera with room to spare.