Velká skála

Velká skála is a protected rock formation in Prague's Troja district, a landmark easy to overlook on the way to the nearby zoo or botanical garden, yet one that carries a striking chapter of the city's geological past. Rising to 314 metres above sea level, it forms the highest point within the cadastral territory of Troja, its elongated silhouette clearly visible along the southeastern edge of the Bohnice housing estate.

What makes this rock formation special?

The protected area covers a modest 1.8 hectares, ringed by a 50-metre buffer zone. The rock body itself stretches roughly 500 metres in length and 40–50 metres in thickness, built from extremely hard Precambrian silicite (buližník) rock laced with quartz veins. That hardness is the key to its survival: while softer surrounding rock eroded away over millions of years, Velká skála remained standing as a resistant landscape feature.

How did the rock form?

The geological story behind Velká skála is unusually eventful. The mass originated at the end of the Precambrian, roughly 600 million years ago, as a siliceous sediment deposited on the floor of an ancient sea. Since then, the site has twice functioned as an island — once during the Paleozoic era and again during the Mesozoic — each time submerged and later re-exposed through cycles of erosion. This repeated flooding and resurfacing makes the outcrop a valuable record of the region's deep geological history. Geomorphologically, it belongs to the Prague Plateau, within the Kladno Table sub-unit.

Why was it protected?

Velká skála was formally declared a nature monument on 29 April 1968 by the former National Committee of Prague. It is now classified under IUCN Category III as a natural monument and carries the official registration code 494. The site is managed by the Prague City Hall.

What grows on Velká skála?

The slopes originally supported remnants of rocky steppe vegetation typical of dry, nutrient-poor, sun-exposed habitats. Over time, non-native species were planted here, including larch, black locust, and black pine. Black locust in particular has proven problematic: it fixes up to 30 kg of nitrogen per hectare annually and releases compounds that suppress the growth of understory plants, crowding out native species. Current management therefore focuses on removing these non-native trees while encouraging native oaks, hawthorns, and hornbeams to reestablish. The herb layer includes heather, fescue grasses, and bellflowers, and annual summer mowing keeps aggressive species in check, giving rarer plants a chance to persist.

Where does the name come from?

The name "Velká skála" (Great Rock) refers back to a neighbouring formation once known as "Malá skála" (Small Rock), which was almost entirely removed by quarrying and has since largely disappeared. Only a small park in the Bohnice district remains as a trace of it today.

Frequently asked questions

Where exactly is Velká skála located? In the Prague 8-Troja district, along the southeastern edge of the Bohnice housing estate, at an elevation of 284–314 metres above sea level.

How large is the protected area? 1.81 hectares, plus a 50-metre protective buffer zone around the monument's boundaries.

Since when has Velká skála been protected? Since 29 April 1968, when the National Committee of Prague declared it a nature monument.

How does it differ from Malá skála? Malá skála was a smaller, neighbouring rock formation that was largely quarried away — today only a small park remnant survives in Bohnice — while Velká skála endured thanks to the exceptional hardness of its rock.