The weirdly-shaped features you see on the floor of this cave are quite unusual. This photo comes from Grotto di Castellana or the Castellana Caves in southern Italy.
Like most caves, the rocks are limestones. These were deposited about 90 million years ago in the Tethys Ocean; the great seaway that once separated Africa and India from the rest of Asia. The closure of the Tethys seaway has driven faulting and mountain building from Spain to China and in this place brought the limestones to the surface.
Erosion of limestone often leads to cave formation. Limestone dissolves easily when exposed to water, formation of a small pool of water on exposed limestone can start the long process of erosion that eventually leads to a cave.
One of several distinguishing features of this cave is the shape of the stalagmites (or speleothems – a more general term for any structures created by dripping water in a cave setting). Normally, dripping water builds stalagmites as vertical pillars, but here, these have grown in many directions. It’s not quite clear why these pillars have grown this way, but it probably involves variable wind flows in the cave that push water droplets around and changing water levels over time, which combined to prevent the formation of the classic vertical structures and cause the stalagmites to grow outwards instead of upwards.
Image credit: EGU Open Access, Deaa Alwanny