The Hidden World Below: 23 Surprising Facts about Caves

Am-Phu cave in Vietnam is decorated with "hell" themes: sculpted demons "and fanged devils bathed in sinister red light, where hands reach up from the waters below and river monsters threaten to gnash (visitors') souls to bits." It's located under the mountain associated with heaven.

The Bracken Bat Cave in Texas has the largest known bat colony in the world. Over 20 million bats live in the cave, which is more bats than there are people living in Mumbai, India, one of the world’s largest human cities.

Wolf Cave a.k.a. Susiluola is a cave in Finland which claims to have evidence of Neanderthals living there pre-Ice Age. It is the only known place to have such evidence in Nordic countries.

The oldest known figurative painting was discovered in a cave named Lubang Jeriji Saléh Cave on Borneo island, Indonesia: a depiction of a bull has been dated to be 40,000 years old. It is unknown which species of humans created the paintings and what happened to them.

There exists a cavern named Marvel Cave in Missouri that’s so large that in 1994 five hot-air balloons were flown simultaneously inside it.

The earliest known modern human fossils found outside of Africa were in Apidima Cave in Southern Greece. These fossils are somewhere between 170,000 and 210,000 years old.

Massacre Cave is a cave on a small island in Scotland. When the Clan MacLeod attacked the Island, all 395 of the islanders hid inside the cave. When the MacLeods found them, they made a fire at the cave mouth and allowed the smoke to suffocate everyone inside.

The oldest known human-made structure is in the Theopetra cave in Greece. This is a stone wall constructed over 23,000 years ago yet the cave itself was occupied by humans from about 135,000 BC.

There is an underground cave in the Dolomite Mountains in Italy where a Consortium of fruit growers store 40,000 tons of apples inside.

While exploring a historic 1900s guana mine, cavers uncovered the largest limestone cave (Lechuguilla Cave) in the United States. Not only did the cave stretch more than 120 miles but it also held a 20-feet gypsum chandelier and rare rock-eating bacteria.