Grotte di Castellana in Castellana Grotte

You're standing at the Castellana Caves, a huge cave system hidden beneath the Apulian countryside, about a kilometre south of the town of Castellana. Have a look around. Everything here sits on limestone, and that limestone has quite a story. Roughly a hundred million years ago, Apulia lay under the sea. Shellfish and sea plants died, sank to the seabed and, over millions of years, were pressed into layers of rock kilometres thick. When the land slowly rose, it cracked. Rainwater seeped into those cracks and dissolved the limestone, bit by bit. Cracks became tunnels, and tunnels became caverns.