They are underground karst caves located in Castellana Grotte, in Apulia (Southern Italy). They date back to 90 millions years ago but they were first explored in 1938. They are at 330 m above sea level and extend for about 3 kilometres.
They have got astonishing stalactites and stalagmites which look like animals like the owl or human figures like the Little Virgin Mary.
The natural entrance to the caves is an enormous chasm sixty meters deep called the Grave. The caves and chasms have mythological or fantastic names like the Balck Cave, the She-wolf cave, the Owl cave, the underground Grand Canyon (of a reddish color due to the presence of iron minerals in this stretch), the Red Corridor, the Dome Cave, the White Grotto, which is bright and shining.