Čertova zeď National Nature Monument

The Čertova zeď – Devil’s Wall NNM was declared in 1964 and lies close to the villages of Smržov, Kotel and Zábrdí and between the town of Český Dub and the village of Osečná in the north-western foothills of the Ještěd mountain ridge and in the Liberecký kraj - Liberec Region. The protected area covers an area of 19.08 hectares, covering an elongated area with a north-east to south-west orientation, and lies at elevations of 450-494 metres above sea level. The basic conservation subject is a fragment of a unique geological formation – an extensive basaltic vein which rises above the surrounding Mesozoic sandstones.
Tectonic movements in the Tertiary period led to fissures in the Mesozoic (Middle Turonian) sandstones of the Bohemian Cretaceous Basin opening up. These fissures were then filled with magma. After this magma cooled it formed basaltic rocks – melilitic olivinite nephelenite, which gradually emerged as a result of weathering of the surrounding sandstones. A real “wall” was formed in this way and is built of horizontal basalt columns of 2-3 metres in width, up to 20 metres in height and an unbelievable 28 kilometres in length running from Mazova horka on the slopes of Mt. Ještěd to the town of Bělá pod Bezdězem. The sandstones which are in contact with the basaltic rock seam are burnt, which can be seen in trenches where basalt was quarried.
The forest stands around the Devil’s Wall are of low quality and Scots pines predominate. Deciduous trees, such as beech, grow in the surroundings on localities which are richer in nutrients. Some parts of the protected area have a well-developed shrub layer with herb vegetation. The actual “wall” plays host to a number of thermophilous plant species.
This basaltic seam was so high and so long that it was necessary to break through it in a number of places to build roads, or even to tunnel under it (the former Čertova brána – Devil’s Gate). The building of roads in modern times led to the destruction of large sections of the wall, which were removed and ground up into roadstone, while whole columns were used as kerbstones. Deep trenches can still be seen in the sandstone in many places where the basalt was removed.
Efforts to protect the unique Devil’s Wall had begun many years earlier but quarrying was finally stopped in 1931 after the state bought a part of the lands. The last remnants of the Devil’s Wall, which are only a few hundred metres long, as well as quarry pits, are now protected.
The Devil’s Wall got its name from the legend, according to which it was built as a result of a bet between a man and the devil, with the rest of the rocks being used to build the Bezděz castle. Václav Hájek of Libočany offered a different version in his Bohemian Chronicles, where he wrote that the wall was built by Prince Mnata of the Přemyslid dynasty in 798 AD to protect his lands against his enemies.