The Kokorinsko region is not only one of the most beautiful parts of the Melnicko region but of the entire Bohemia. The landscape has a canyon-like appearance and in the northern part it changes into hill country with the Vratenska hora as the summit. The entire Protected Zone was in the past called the Polomene hory (Broken Mountains). The Kokorinsky dul Protected Zone welcomes many tourists ever year. It is located along the Psovka stream and has a number of sideway gorges. This area is typical for sandstone rocks of different shapes - overhangs, small caves, niches and cornices. The Polomene hory, similarly to the Czech Middle Earth, developed at the end of the Tertiary when the relief broke and basalt and phonolite magmata penetrated to the surface.

The Prolomene hory are made up of mainly Mesozoic sandstone blocks formed in a way that makes them stand out of the surrounding area with a rather monotonous surface. The sandstone is mixed with different binders. Furthermore, you would find here claystone and siltstone. The Tertiary intrusive rock include trachyte, phonolite and basalt.

The reason for establishing the Protected Natural Zone here was the existence and number of various sandstone surface shapes, as the relief and rock foundation were the decisive factors of the natural and social environment in this area. The Polomene hory represent a unique type of sandstone relief that is not found in any other area in Czech Republic.

The Kokorinsky dul is the heart of the Kokorinsko Protected Zone that has the area of 265 km². It is the best place in Europe where first signs of sandstone block disintegration were found. These rather soft rocks were on the bottom of ancient sea that was here at the end of the Mesozoic. External geological phenomena caused weathering and disintegration that resulted in interesting shapes as lids, cells, rock windows, rock gates, cornices and niches.

The layout of the valley is very much dependant on the paths of cracks. The most typical canyons go from north to south, or east to west. More extensive volcanic knots created the inclining radial valley network.

Geomorphologic-important elevations of various shapes and sizes created penetrations of neovolcanic objects of basalt and phonolite rocks, originally undersurface, that were pushed up by the denudation process, so as at some areas there are the dominant relief parts.

Rock formations Obri hlava and Zaba