In this cover from Slovakia the stamp on the right depicts a picture of the National Park Poloniny, a part of the UNESCO World Heritage site
Ancient and Primeval Beech Forests of the Carpathians and Other Regions of Europe. This site comprises undisturbed examples of temperate forests that demonstrate the postglacial expansion process of European beech from a few isolated refuge areas in the Alps, Carpathians, Dinarides, Mediterranean, and Pyrenees. The site was originally listed in 2007 as the Primeval Beech Forests of the Carpathians, shared by Slovakia and Ukraine, extended in 2011 to include the Ancient Beech Forests of Germany, and further extended in 2017 and 2021 to include forests in a total of 18 countries. Four reserves in Slovakia are listed, Stužica – Bukovské vrchy, Rožok, Vihorlat, and Havešová. The modification of the boundaries of forests in Slovakia took place in 2021.
