Surface of Čertova kazatelna at Plešivec
Ordovician quartzites of Brdy often form distinct parties of local hills, "brdo" used to be a term for a long rocky ridge in Old Czech. Rocks, whether revealed by nature or human work in many old quarries, are worth watching. Sometimes smooth quartzite flats easily turn into vein-crossed surfaces, various colors appear introduced by iron ingredients and lichens. Rusty, blue-greyish and green areas appear on white-greyish background. Quartzites are rugged on touch but also smooth, strange distant cousins of limestones by spirit, if not by composition.