Růžák National Nature Reserve was declared on 29th December 1973 in the parishes of Růžová and Srbská Kamenice in the Ústecký kraj- Ústí nad Labem Region. The NNR covers an area of 116 ha and covers a distinctive basaltic cone, which is covered by natural mixed forest stands, which are of a primeval character in some areas. The entire NNR lies within the first zone of České Švýcarsko National Park. The peak of Růžák lies at 619 metres above sea level and is the highest point in the national park.
The characteristic cone of Růžák is a typical example of a denuded relict of the North Bohemian tertiary volcanism. The core of Růžák is built of basaltic effusive rocks which are exposed in the summit area and in places displaying the typical six-sided prismatic jointing in the form of columns of basaltic minerals. Extensive talus fields formed of broken columns of basaltic minerals can be found on the slopes of the hill. The mummified cone of Růžák was originally surrounded by cretaceous sandstones, which were gradually eroded away. Not all of the sandstone was carried away and it remains in several places on the hill slopes, making these the highest bodies of sandstone in the national park. Růžák NNR is a massive and distinctive cone which is visible from all directions and dominates the landscape.
Extensive mixed forest stands of a primeval character have been preserved in the NNR. The most valuable forest stands are the herb-rich beechwoods (Melico-Fagetum), in which beech (Fagus sylvatica) dominates and the sub-montane talus and ravine forests (Mercuriali-Fraxinetum) with sycamore (Acer pseudoplatanus), Norway maple (Acer platanoides), wych elm (Ulmus glabra), large-leaved lime (Tilia platyphyllos) and European ash (Fraxinus excelsior). Typical species which are found in the herb-layer include nine-leaved toothwort (Dentaria enneaphyllos), coralroot (Dentaria bulbifera) and spring pea (Lathyrus vernus). On the rocky scree we can find rare lichens such as Vezdaea cobria, which is not found anywhere else in the Czech Republic or the hair-pointed grimmia moss (Grimmia trichophylla), which is on the Red list of mosses of the Czech Republic. A whole range of rare fungi species also occur in Růžák NNR, including the orange chanterelle (Cantharellus friesii) and the bonnet fungus Mycena diosmus.
The largest animals which live in the NNR include red deer (Cervus elaphus) and the roe deer (Capreolus capreolus) and wild boar (Sus scrofa) are also common here. Other vertebrates include the fat dormouse (Glis glis), fire salamander (Salamandra salamandra) and Alpine newt (Triturus alpestris). Less common birds which nest here include Tengmalm’s owl (Aegolius funereus), black woodpecker (Dryocopus martius) and grey woodpecker (Picus canus). Růžák NNR is one of the richest localities in České Švýcarsko NP for its invertebrates and plays host to many rare insect species. Significant beetles living in the NNR include the ground beetle Carabus irregularis and the critically-endangered stag beetle Ceruchus chrysomelinus. The weevil Plinthus tischeri is a notable glacial relict, as it normally occurs high in the mountains along the upper tree line. The false oil beetle Ischnomera cinarascens of the Oedemeridae is also a rare find and indicates the natural origin of the forest biotopes here.
The peak of Růžák and the NNR can be visited by following the yellow marked tourist trail, either from Růžová or from Srbská Kamenice. The summit of Růžák is covered by mature forests and does not offer views over the surrounding landscape.