Orthocerový lůmek

Orthocerový lůmek is a small, abandoned limestone quarry on the edge of the Radotín Valley, within the Prague cadastral district of Lochkov. It lies roughly 250 meters northeast of the cement plant in Radotín, close to the junction of the road connecting Lochkov and Radotín with its branch toward Zadní Kopanina. It is easy to walk past without realizing what it actually is — yet this modest site is one of the more significant geological landmarks near Prague.

Why is this site protected?

The area was declared a protected natural monument in 1977 and covers just 0.5 hectares, at an elevation between 255 and 300 meters. The reason for protection is an outstanding geological profile exposing the boundary between the Kopanina and Požáry formations. This profile is regarded as one of the fundamental reference sections for the international stratotype of the Ludlow–Přídolí boundary, a division within the Silurian system. For geologists and paleontologists, this makes the site far more than a local curiosity — it is a reference point of international importance.

What can visitors see here?

The rock layers exposed in the quarry formed from Silurian sediments and contain a rich deposit of cephalopod fossils, including the straight-shelled orthoceratites from which the site takes its name. It is a productive paleontological locality that offers a glimpse of marine life from hundreds of millions of years ago, when a shallow sea covered what is now the Czech landscape. The strata are visible along a small, rocky face of the former quarry, gradually being reclaimed by vegetation since extraction ceased.

How to get there?

Orthocerový lůmek lies within the Bohemian Karst, more specifically inside the Radotín-Chuchle Forest nature reserve. A marked nature trail, the Radotín Educational Trail, runs around the quarry, making the site easy to reach on foot for anyone exploring the area. The nearest landmarks are the cement plant in Radotín and the road junction leading toward Lochkov and Zadní Kopanina.

Frequently asked questions

Can the quarry be visited independently? Yes, the area is publicly accessible, and a marked nature trail runs alongside it, making orientation straightforward without a guide.

What makes this site special? Its main value lies in the exposed rock layers marking the Ludlow–Přídolí geological boundary and the numerous orthoceras cephalopod fossils that testify to an ancient marine environment.

Is it suitable for families with children? Given its small size and easy access via the nature trail, a walk to the site is manageable for most visitors, though the quarry itself will appeal mainly to those interested in geology and paleontology.

How large is the protected area? The protected area covers only 0.5 hectares, making it one of the smaller but scientifically most valuable protected sites near Prague.