Klausenpass Blockhouse, Military fortress at Klausenpass, Switzerland

The Sperrstelle Klausenpass is a Swiss Army defensive position on both sides of the 1948 m Klausenpass, in the municipalities of Unterschächen and Spiringen/Urnerboden. It held VOBAG 22 prefabricated concrete shelters, U4 spherical bunkers, rock caverns such as Märcherstöckli A 8741, and demolition points on the pass road. From 1966 an infantry works A 8744 with an 8.1 cm fortress mortar covered the barrier.

The blockhouse was constructed by the Swiss Army during the 20th century as part of the country's defense network. It was built during a period when mountain passes were considered essential for national security.

The site's name, Sperrstelle Klausenpass, comes from the Swiss Army's barrier numbering: the pass was long its own barrier, No. 2457, before being merged into the Vorfrutt–Klausenpass barrier, No. 2454, in the late 1980s. The prefabricated VOBAG 22 shelters and U4 spherical bunkers buried here in the 1960s were standard Swiss civil-defence designs, so the same concrete elements appear at barriers across the country.

Summer is the best time to visit, as the road connecting Altdorf to Linthal is typically open and accessible during warmer months. Winter closures mean you should check conditions before planning a trip.

The barrier was reinforced in 1966 with a rock gallery for fortress mortars: an 8.1 cm Festungsminenwerfer 56 with a range of 4 km, housed in infantry work A 8744, which also had to be protected itself. The site was a separate barrier (army number 2457) until the late 1980s, then merged into barrier 2454 Vorfrutt–Klausenpass.