Vosek

Vosek is a small but scientifically notable nature reserve on the Švihov Highlands, north of the town of Rokycany, spanning the cadastral territories of Osek u Rokycan and Volduchy in the Rokycany district of the Pilsen Region. It was declared a national natural monument on 5 September 1989 by decision of the then Rokycany district authority, and today the site forms part of the Barrandien National Geopark. The protected area covers just under 76 hectares at an elevation between 376 and 408 metres.

What exactly does this protected site preserve?

Unlike most nature reserves, Vosek was not set aside for its landscape or vegetation but for a paleontological deposit — silica concretions containing embedded fossils, known locally as "Rokycany balls" (rokycanské kuličky). These formed during the Paleozoic era, in the Middle Ordovician period roughly 465 million years ago, as carbonates precipitated around organic remains on the floor of the ancient sea that once covered the area.

What fossils have been found here?

Inside the concretions, collectors and researchers have found exceptionally well-preserved fossils of Paleozoic organisms. More than 150 species have been described from the site, most commonly trilobites, brachiopods, mollusks and echinoderms — including starfish and brittle stars in a state of preservation rarely seen elsewhere. The earliest documented fossil collections from Vosek date back to around 1840, and among the scientists who studied them was the renowned paleontologist Joachim Barrande.

Why is the site under threat?

The southern part of the reserve was partly destroyed during the construction of the D5 motorway, prompting discussions about redrawing the boundaries of the protected area to reflect its current, surviving extent. Illegal fossil hunting is another ongoing risk: specimens from Vosek are highly prized among mineral and fossil collectors, which has left the site vulnerable to unauthorized digging for decades.

Who should visit Vosek?

Vosek is aimed primarily at geology and paleontology enthusiasts, as well as anyone curious about life on Earth hundreds of millions of years ago. It isn't a conventional tourist attraction with visitor infrastructure or scenic viewpoints — it's a scientifically significant site best approached with an awareness of its fragility and research value.

Frequently asked questions

What are the "Rokycany balls"? They are the local nickname for the silica concretions found at Vosek, which preserve fossils of organisms from roughly 465 million years ago inside their cores.

When did Vosek become a protected area? On 5 September 1989, by decision of the Rokycany district authority at the time.

How many fossil species have been recorded at the site? Over 150 species, mainly trilobites, brachiopods, mollusks and echinoderms.

Is the reserve fully intact today? No — its southern portion was disturbed during construction of the D5 motorway, which led to proposals for redefining the protected area's boundaries.