The Kluže Fortress sits dramatically above the gorge of the Koritnica river, 3 km east of Bovec on the road toward the Predel Pass. The current structure was built by the Austro-Hungarian military in 1882 on the site of earlier Venetian and Napoleonic-era fortifications; its mission was to control the narrow pass into what was then Austrian territory.
The fortress is reached on foot through a concrete tunnel cut into the rock — the same tunnel used by the garrison. Inside, the rooms have been opened to the public as a small museum covering the history of the fortifications and the Isonzo Front fighting in the surrounding mountains. The views down into the Koritnica gorge from the upper gun positions are striking. Open during summer months; check local signage for current hours. Above the fortress, an older Ottoman-era watchtower commands the heights.