Krubera Cave
The difference in elevation of the cave's entrance and its deepest explored point is . It became the deepest-known cave in the world in 2001 when the expedition of the Ukrainian Speleological Association reached a depth of which exceeded the depth of the previous deepest-known cave, Lamprechtsofen, in the Austrian Alps, by . In 2004, for the first time in the history of speleology, the Ukrainian Speleological Association expedition reached a depth greater than , and explored the cave to . Ukrainian diver Gennadiy Samokhin extended the cave by diving in the terminal sump to 46 metres' depth in 2007 and then to 52 m in 2012, setting successive world records of 2,191 m and 2,197 m, respectively. Krubera is one of the two known caves on Earth deeper than 2,000 metres.
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.