Prosecké skály, Sandstone geological formation in Libeň, Czech Republic.

Prosecké skály is a natural monument on the border of Prosek and Libeň in Prague 8, formed by the walls of old quarries cut into Cenomanian sandstone of the Czech Lower Cretaceous; no natural rock outcrops are exposed here. The open profile shows a lower light, crumbly white sandstone laid down in freshwater and an upper coarse, rust-coloured sandstone deposited in a marine environment. The massif is cut by faults and by blocks sliding downslope, and it holds vertical pseudokarst cavities and black silicate pebbles.

The site was designated as a protected natural monument in 1968 and serves as a reference profile for studying Peruc and Korycany rock formations. This protection recognized its importance for understanding the geological development of the area.

The name Močálka refers to the flooding of the Hampl quarry tunnels by sewage from a broken sewer. Workers hand-quarried white kaolinic sandstone with a spike, following the softest water-soaked seams along fissures, so the passages resemble natural caves rather than a mine.

Access is available through a marked hiking path that is fairly easy to locate. The nearest public transportation stops are about 250 meters away, requiring a short walk from the station.

The sandstone walls contain black silicate deposits and fossilized plant remains that provide insights into the development of the Czech Cretaceous Basin. These geological features make the location valuable for understanding ancient environmental conditions in the region.