Sigmund-Thun-Klamm, Slot canyon in Kaprun, Austria

The Sigmund-Thun-Klamm is a gorge up to 32 metres deep and 320 metres long in the municipality of Kaprun, cut by the Kapruner Ache, a stream fed mainly by glacial meltwater from the Hohe Tauern. Its dark grey rock walls rise vertically on both sides, and at the upper end water pours over a ledge in a white, foamy fall. A weathered wooden pole leans diagonally across the upper section.

The canyon took shape roughly 14,000 years ago when Ice Age glacial meltwater carved deep channels into the surrounding mountains. This ongoing process of water erosion continues to shape the landscape visitors see today.

The gorge is named after Sigmund von Thun-Hohenstein, a former governor of Salzburg. A toll, the Klamm-Maut, is collected from visitors using the wooden walkways, which are open only in the summer months, to fund their upkeep and maintenance.

The gorge is only open during the summer months, and a toll is charged for using the wooden walkways, which pays for their upkeep. The route ends at the Bürgsperre dam and the Klammsee reservoir. The rock is wet from the spray of the Kapruner Ache, so wear shoes with grip.

The gorge ends at the Bürgsperre dam, which holds back the Klammsee. The wooden pole leaning against the rock wall in the upper section is a remnant of the old walkway construction. The gorge is up to 32 m deep and 320 m long.