The medieval fortress rises fifty metres above the old town on a granite outcrop that makes it look nearly impregnable — which for much of its history it was. The complex dates to the thirteenth century and was expanded repeatedly until the sixteenth. Visitors reach it by funicular from the town centre and can explore the keep, the round tower, the inner courtyard, and the museum of local history. The Heroes' Organ — the largest outdoor organ in the world — is housed in the fortress and plays a brief automated recital at noon daily, its sound rolling across the Inn valley like something from another age.
The fortress museum covers the military history of the site, including its role as a state prison in the nineteenth century — the cells held notable inmates including the Tyrolean freedom fighter Andreas Hofer after his capture by Napoleon's forces. The views from the ramparts over the Inn gorge and toward the Wilder Kaiser peaks are excellent. The fortress is open daily from April to October and on weekends in winter.