Castellana

The story of the Grave begins in the Upper Cretaceous (ninety-hundred million years ago), when Puglia was covered by an ancient sea, where large colonies of shellfish and sea vegetables lived. For millions of years, generations and generations of these life forms succeeded to each other, and dying, their empty shells and their carcasses had accumulated on the sea floor, making a gigantic deposit of mud and sand, that with its slow but continuous growth was gradually compressed, to form one limestone layer several kilometers thick. From sixty-five million years ago, the gradual raising of the lands brought the region to its current appearance and in the emerged limestone mass, because of its rigidity, extended fractures had formed, that strongly engraved it. River water of heavy precipitation, percolating into the ground, then had formed a huge underground aquifer, as to gradually dissolve the limestone and extend the fractures; these had come to join each other thanks to the collapse of the interposed rock, forming, this way, small ducts, gradually turned into ever-widening circles. In places where fractures intersect each other in large numbers (a phenomenon here more relevant than in any other point of the karstic system of Castellana) arose extended and repeated collapses; these expanded themselves more and more upwards, gradually reducing the thickness of rock separating the cavity from the outside, as long as the residual layer, now thinned, had not collapsed, making reach inside the cave the first ray of light.