Krňov

Krňák, also known as Krňov, is a nature monument in the southern part of Prague, in the Lahovice area beneath Zbraslav Castle. The protected site covers a dead arm of the Berounka River, now a pond, together with adjoining meadows, floodplain forest, and a stretch of the Vltava riverbank running from Lahovice to Strnady. The Lipanský stream also flows through the area.

How did this place come to exist?

The pond's present shape is the result of a long history of shifting river channels. The original bed of the Berounka once ran through Lipence and continued beneath Zbraslav. Between the 12th and 14th centuries a branch channel formed, and in 1829 a flood redirected the river's main current toward Lahovice. After 1845 the old channel gradually lost significance, and the flood of 1872 finally silted it up, creating the dead arm that survives today.

How long has this site been protected?

Krňák was declared a nature monument on 1 September 1988 by a decision of Prague's National Committee. The protected area covers roughly 27.6 hectares and falls under IUCN Category IV, designated for habitat and species management.

What lives and grows here?

The site hosts a mosaic of wetland and riverside habitats: alder and black poplar floodplain forest with willow, maple, hornbeam, and oak, alongside dry, xerothermic grasslands on gravel banks along the Vltava. Protected plant species recorded here include bristle club-rush, mudwort, and brown flatsedge.

Amphibian populations — including edible frogs, brown frogs, and common and green toads — have declined noticeably in recent years. Reptiles found on site include the common lizard, slow worm, grass snake, and adder. Water birds such as the Eurasian coot nest on the pond, along with reed-dwelling songbirds.

What else is worth knowing about this place?

Road infrastructure cuts through the protected area: route I/4 was built through it in 1966, followed later by route II/102, both fitted with culverts that allow water to pass freely. A reinforced-concrete bridge, built between 1911 and 1913, spans the old riverbed on the site of a wooden bridge that had stood there since 1810.

Frequently asked questions

Where exactly is Krňák located? In the southern part of Prague, in the Lahovice district below Zbraslav Castle, at an elevation of 191 to 210 metres above sea level.

How large is the protected area? The Krňák nature monument covers approximately 27.6 hectares.

Since when has Krňák been legally protected? Since 1 September 1988, by decision of Prague's National Committee.

Does a road run through the reserve? Yes, routes I/4 (built in 1966) and II/102 cross the site, both equipped with culverts for water flow.

What species of plants and animals can be found here? Protected plants such as bristle club-rush and brown flatsedge, along with lizards, slow worms, grass snakes, adders, and water birds like the Eurasian coot.