Just three kilometres north of Mělník lies a quiet natural monument hiding a network of old underground quarries carved into marlstone. Vehlovice Marlstones is a fascinating stop for anyone curious about geology, fossils, or bats, combining a slice of mining history with a rare glimpse into the Cretaceous seas that once covered this region.

The site has a rugged, low-key atmosphere - overgrown quarry entrances, exposed rock layers telling the story of ancient sedimentation, and a stillness that makes it feel like a hidden corner of the countryside. In winter, the old tunnels become a refuge for several bat species, including the lesser horseshoe bat, so the underground passages stay closed to visitors during colder months. It is not a long hiking destination but works well as a short, interesting detour on a day trip around Mělník.

• Mělník - about 3 km to the north, easy walk or bike ride on flat terrain
• Vehlovice village - the closest access point right next to the protected area

• The underground galleries are secured with a grille and closed to visitors, as they serve as a winter roost for bats and horseshoe bats
• Protected since 2002, the site is managed by the Central Bohemian Regional Authority

Fossil fish, crayfish, and mussels dating back tens of millions of years have been found in these old quarries, and the yellowish marlstone once mined here, nicknamed the 'egg yolk', was used to make paving slabs and troughs across the region.