The 17k stamp was issued in 2009 featuring the diversity of the night-time forest beauty of the Křivoklátsko biosphere reserve.
In 1978 the Křivoklátsko region was proclaimed a protected land area of 628 km2 located in the territory of the Central and the West Bohemian regions. On March 1, 1977 this area, due to its high natural values, was proclaimed a UNESCO biosphere reserve. Two thirds of the area are covered with leafy and mixed forests. The highest point of the Křivoklátsko is the Těchovín hill (616 m above sea level). The lowest point is the Berounka river level at the place where it leaves the area (223 m above sea level). This river has greatly affected the formation and preserved character of the whole area. For thousands of years the river flow cut deep into the valley whose steep-sloped hillsides are covered with natural vegetation of various formation, pervaded in some places with natural exposures with xerothermal fauna and flora. The layers of sediments in the vast meanders of the river led to the creation of river terraces. In most of the year the temperature at the bottom of the valley is very low, which corresponds to the conditions of submountain to mountain regions. Temperature inversion, a phenomenon typical of the Křivoklátsko region, is one of the main causes of the great diversity of species. The preserved species include over 1,800 species of vascular plants, at least 52 species of wood plants, more than 120 species of birds and a number of other animals, of which 20 species are critically endangered (e.g. Ascalapus libelluloides, Schaeff., fish hawk, Austropotamobius torrentium, freshwater-lamprey), 37 heavily endangered (e.g. large mouse-eared bat, barn owl, black stork, nightjar, agile frog) and 44 endangered (e.g. eagle owl, Trichius fasciatus, Carabus irregularis). The symbol of the Křivoklátsko protected land area is red deer kept in the Křivoklátsko forest enclosures from time immemorial.