The distinguishing feature of inanimate nature in the Northern Velebit National Park is the beautiful karst landscape which is characterized by numerous peaks, big and small, regularly and irregularly shaped sinkholes and dolines, mountain grasslands and karst fields. This majestic karst topography, created through dissolution of carbonate rocks (limestone and dolomite) by the action of carbon-dioxide rich water, was one of the main reasons for proclaiming Northern Velebit a national park.
Walking through the National Park, you can easily see countless smaller karst forms which inscribe almost every rock along educational and mountain trails like the most stunning calligraphy. These numerous small and sometimes large corrosion forms are called karrens.
However, beneath the surface an equally interesting subterranean inanimate world is hiding, consisting of countless underground hollows. The best known are vertical caves (pits). Thanks to the discovery of these pits, the Northern Velebit National Park, notably Hajdučki i Rožanski Kukovi strict reserve, has been ranked among the most interesting speleological regions in the world. So far three vertical caves over 1000 meters, the deepest in Croatia, have been discovered and partly explored in the heart of the National Park.
Owing primarily to the geological diversity of the Northern Velebit National Park area, preconditions have been created for the development of a large number of diverse habitats and ecosystems. They are home to numerous fungal, plant and animal species that have become adapted through evolution to exceedingly harsh climatic conditions existing in this area.