Velebit
There are hundreds of "holes" on Velebit. It has the largest and deepest caves in Croatia. The three-part "Lukina jama" cave is 1392 m deep, making it one of the deepest caves in the world, and the deepest in southeast Europe, while the "Slovačka jama" is 1320 m. What makes it unique is that it is completely vertical, steepest in the world. At the bottom of the pothole is a water course or siphon with branches that are still unexplored. A kind of leech was discovered in the pothole, which has been ascertained to represent a new species, genus and family; it has been named "Erpobdella mestrovi".
Castellana Caves
The Caves of Castellana open in south-eastern Murge, a limestone plateau dating back to the upper Cretaceous (ninety- one hundred million years ago) and rising 330 metres above sea level.
The area of Castellana is characterized by limestone, a sedimentary rock composed largely of calcium carbonate, known as Limestone of Altamura.
The cave system is 3348 metres in length and the point of maximum depth reaches 122 metres. The temperature within the caves is about 18 °C.
The caves are open all year round except for Christmas Day and the New Year’s day. The visit develops along two itineraries: the first is 1 km long and lasts about 50 minutes while the second is 3 km long and lasts about two hours. The tour timetable changes depending on the season. In addition, during the summer there are also guided night tours.
The Grave is the first and the biggest cave of this wonderful speleological complex and it is the only one communicating with the outside. It measures 100 m in length, 50 m in width and 60 m in depth. Going beyond the Grave stalactites, stalagmites, curtains and precious crystals continues to embellish everywhere the caves. The name of the environment are the result through the imagination of the early explorers: the She-Wolf, the Monuments, the Owl, the Little Virgin Mary, the Altar, the Precipice, the Desert Corridor, the Reverse Column, the Red Corridor, the Dome up to the last and the most dazzling one, the White Cave.