The Northern Velebit National Park area, notably Hajdučki Kukovi and Rožanski Kukovi strict reserves, are ranked among the most interesting speleology sites in the world.
The largest number of speleological features are found in Velebit breccias, rocks formed as a result of strong tectonic activity which caused the decomposition and destruction of existing deposits and structures. Through destruction and landslides, subsequent sedimentation in karst depressions and hardening of rock fragments new sediments were created, today referred to as Velebit breccias. Over millions of years they were gradually uplifted along faults thereby forming beautiful Hajdučki Kukovi and Rožanski Kukovi karst peaks.
The pits of Northern Velebit are continuously being explored by numerous speleologists from various speleological societies from Croatia and abroad. Each year, their research yields new insights into the wealth of underground karst forms of Velebit.
Due to their characteristics, speleological features found in these rocky peaks have been recorded in world’s caving literature.
In the Northern Velebit National Park area as many as 500 speleological features have so far been discovered, of which 98 percent are pits. Pits are typical underground karst formations with vertical or sharply inclined shafts with an incline of over 45°. Northern Velebit is home to four pits with a depth of over 1000 meters.
Lukina jama – Trojama – with a depth of 1431 meters is listed among the deepest pits in the world.
Patkov gušt – with 553 meters is the second deepest vertical shaft in the world extending from entrance to the bottom of the pit.
Velebita – with 513 meters is the deepest underground vertical shaft in the world, having a total depth of 1026 meters.
Meduza – the second deepest underground shaft in the world (450 meters), second to Velebita pit, has been explored up to a depth of 707 meters.
Slovačka jama - the second deepest pit in Croatia, has been explored up to a depth of 1324 meters. A large population of Velebit leech and many other animals have been discovered in this pit.
Nedam - pit is deep 1021 m and was explored in 2019.
Pits are home to unusual living organisms that are adapted to life in complete darkness. Among them is the Velebit leech (Croatobranchus mestrovi), so far discovered in only four deep pits within the Northern Velebit National Park.
To learn more about the pits of north Velebit, visit the Croatian Speleology website.