Štola Stradonice, Natural monument in Peruc, Czech Republic

Štola Stradonice is a protected natural site on the southern edge of Peruc village. It sits on terrain between 190 and 220 meters in elevation and displays rock faces with yellowish-gray sandstone layers.

The tunnel was driven to test the kaolinic refractory clays of the Upper Cretaceous Peruc Formation, made of marlstones, claystones and sandstones. Its main gallery runs about 150 m with four shorter side galleries, under 30–40 m of overburden. The site has been protected since 1999.

The name štola denotes an adit, the horizontal mining passage driven to test the kaolinic refractory clays of the Peruc formation. Since 1999 the 10.05-hectare site has been protected as a natural monument, valued today as the Louny district's only known permanent bat hibernaculum rather than as a mine.

The tunnel entrance lies in a slope about 30 m above the Débeřský stream, left of the forest road from Stradonice to Peruc, roughly 500 m southeast of Stradonice. A yellow-marked hiking trail and cycle route 202 pass the site; the nearest station is Pátek, about 2.5 km away. The entrance has a locked grille and the tunnel is not open to the public.

The tunnel is the only known permanent bat hibernation site in the Louny district, and the lesser horseshoe bat (Rhinolophus hipposideros) is the most numerous species there. Six endangered bat species hibernate behind the locked grate, which is why entry requires permission from the nature protection authority.