Čertova zeď

Čertova zeď ("Devil's Wall") is a modest but geologically remarkable hill, 337 metres above sea level, in the Liberec Region's Česká Lípa district, within the cadastral area of Ploužnice pod Ralskem, roughly 4 km southeast of the town of Mimoň. The name describes a striking wall-like rock ridge formed by a hard basalt vein cutting through soft sandstone. It's one of several Czech rock formations sharing this name, so it's easy to mix it up - a better-known Čertova zeď (a protected nature monument) lies near Český Dub, in an entirely different part of the region.

How did this rock wall form?

The formation is a remnant of a Tertiary basalt dike: molten rock once forced its way into a fissure within Cretaceous sandstone and hardened there. Over millions of years, erosion gradually stripped away the softer surrounding sandstone, leaving the tougher basalt standing exposed as a wall-like ridge. The surviving fragments of Čertova zeď are considered among the finest examples in the entire Czech Republic of horizontal columnar jointing in basalt - the distinctive, organ-pipe-like cracking pattern that forms as molten rock cools and contracts.

The dike originally ran for several kilometres, but decades of quarrying for building and road stone removed most of it. Only scattered remnants of the original wall survive today.

What else is there to see nearby?

A trail runs from a crossroads below the wall, past the hill known as Kotelský vrch, alongside a rock feature called Čertův stolec ("Devil's Chair"), and on to the site of a now-vanished rock gate, Čertova brána. Close by stands the Kotelská lípa, a linden tree reputed to be roughly a thousand years old and one of the oldest trees in the region. The site is part of the educational network run by Geopark Ralsko, which organises multi-hour field programmes here for school groups, explaining the local geology and landscape history.

How do you get there, and is it tourist-friendly?

You can drive as far as the nearby village of Hvězdova; beyond that, only forest roads and paths lead to the site. This is genuinely a walking destination rather than a developed attraction - there's an educational trail, but little else in the way of tourist infrastructure. It's worth remembering that the surrounding area was part of a closed military zone for decades, which kept it off-limits to visitors until the early 1990s.

Ralsko - from military training ground to geopark

The wider area takes its name from the former Ralsko Military Training Area, closed to civilians until 1991. After the army withdrew, the land was gradually opened to the public, and in 2016 it was granted the status of a national geopark - Geopark Ralsko, covering more than 294 square kilometres of the former training grounds. A large part of the region also falls within the Kokořínsko - Máchův kraj Protected Landscape Area (its Doksy section) and the Natura 2000 network. Today the area is crossed by dozens of kilometres of hiking and cycling trails, making it a popular destination for families and nature lovers who come both for the flat, easy terrain and for traces of the region's unusual military past.

Frequently asked questions

How is this Čertova zeď different from the other one with the same name? The Czech Republic has several rock "devil's walls" formed by similar basalt dikes. The one near Mimoň and Ralsko is a separate site from the well-known Čertova zeď near Český Dub, despite the identical name and comparable geological origin.

Can you climb on the formation or walk right up to it? A hiking trail runs along and near the formation through forest paths; there's no developed climbing infrastructure here, and the site is oriented mainly toward education and nature observation.

Why does the basalt form regular columns? It's the result of magma cooling slowly inside a rock fissure - as the rock contracts, it cracks along regular planes, producing the distinctive polygonal columns visible on the exposed sections of the wall today.

Is Ralsko still a military area? No. The former training ground was closed to the army in 1991, and much of the area now functions as a geopark and recreational destination, though its military history remains part of the region's identity.