Borra Caves are ancient structures ripe with stalactites and stalagmites. They are considered to be the deepest in India. The stalactites and stalagmites in the caves have various shapes- formations resembling Shiva-Parvati, Mother and Child, the beard of a saint, a crocodile and even a stalagmite in the shape of a human brain. There is also a naturally formed Shivalinga deep inside the cave. Tribal people in the surrounding areas (Jatapu, Porja, Kondadora, Nookadora) throng the caves to pray to the linga every Shivaratri. They narrate dramatic tales of the history of the caves and the legends associated with them in Telugu, English, Hindi, Bengali and Oriya. The caves were discovered by British geologist William King when he was on one of his expeditions in 1807. These caves are believed to be over 150 million years old. They were carved out by small streams that flow into the Gosthani River. Humic acid in the water reacted with the calcium carbonate in the limestone of the hills, and gradually broke down the rocks. Anthropologists found tools made of stone, belonging to the Middle Paleolithic Age (30,000-50,000 years ago), indicating human habitation in the surrounding areas. The cave derives its name from a hole in the roof over its central area (borra means a hole in Oriya). The main entrance to the cave is at an altitude of 705 m above sea level while the lowest point lies at 625 m. The total length of the caves is about 200 m. The Dandakaranya-Bolangir, Kibur railway track runs over the Borra Caves. Several small stalls, set up outside the cave entrance by local tribes sell souvenirs such as mugs made from the bamboo shoot, hats and spices grown in Ananthagiri Hills. AP tourism has a Haritha restaurant here, which serves lunch and refreshments to tourists.