There is a cave in Romania named Movile Cave that had been sealed off from the outside world for 5.5 million years and scientists have discovered dozens of unique lifeforms thriving in the poisonous gases and water.
2. A set of footprints of a young child and a wolf or dog walking side by side was found in the Chauvet Cave in France. This information suggests the origin of the human-dog companionship could date to before the last Ice Age.
3. Hang Sơn Đoòng, one of the largest caves in the world which is in Vietnam is so big that it has its own river, jungle, and climate.
4. When French explorers thought they were the first Europeans to ever reach some historical Afghan caves in the 1930s, they were surprised to find a text inscribed on the wall saying: "if any fool this high samootch explore, Know Charles Masson has been here before."
5. A skeleton from 7150 B.C. found in 1903 in an English cave (Gough's Cave) was recently found to be a DNA match for a history teacher living nearby.
In 1992, a youth group descended into the Bruniquel Cave in France with steel brushes to remove graffiti and ended up partially removing 15,000-year-old bison cave paintings.
7. In the Blue Lake Rhino Cave in Washington State there is a 14.5 million-year-old cast of an early Rhino ancestor about 300-feet up the side of a cliff, which was created when basalt lava slowly covered the corpse floating upside down in an ancient lake.
8. Three Boys explored a small cave (Lummelunda Cave) in Sweden using matches and planks every Sunday. After regularly exploring for two years, in 1948, a stone fell and opened a passage into a much larger cave system. The first hall after the passage was named “The Mountain King’s Hall.”
9. The Giant Crystal Cave in Mexico, with crystals weighing up to 50 tonnes, had an average of 100% humidity and 58°C temperature. This meant that the coldest place in the cave was the lungs, so water would condense in it, and exposure for over 10 minutes would lead to death by drowning.
10. In 1839, Dr. John Croghan bought Mammoth Cave in Central Kentucky and turned it into a tuberculosis hospital. It was a massive failure and Dr. Croghan died of Tuberculosis.
An underwater cave named Cosquer Cave in southern France has more than 20,000-year-old cave art on its walls, which were probably made when the sea levels were lower. The art depicts Auks, Bison, wild horses, and more.
12. All of the world's four deepest caves are located in Abkhazia in Georgia. The record-holder is Veryovkina Cave, which goes down at least 1.3 miles. Due to the hazards and need for specialized rope techniques, “the round trip —top to bottom and back— takes professional speleologists about a week.”
13. The oldest known sewing needle is 50,000 years old. In 2016, scientists in Siberia found an ancient sewing needle in a mountain cave. It was made from the bones of a large and unidentified bird.
14. The Cave of Swallows in Mexico is the largest cave shaft in the world, being almost 1,000 feet wide at the bottom and 1,100 feet deep, and it's home of many birds, but despite its name, almost no swallows.
15. In June 1836, a group of boys in Arthur’s Seat, Scotland found 17 small coffins with tiny dolls inside in a cave. Their origin is still debated but theories include witchcraft, burial superstitions and them being a tribute to the 17 victims of the notorious "body snatcher" serial killers.
16The Door to Hell
In 1971, Soviet geologists tapped into a cavern of natural gas. The ground beneath the rig collapsed, leaving a hole 70 m across. To avoid a release of harmful gas, they lit it on fire, thinking it would burn off in a few days. 41 years later it is still ablaze. Locals call it "The Door to Hell."
17. 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.
18. 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.
19. 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.
20. 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.
22. 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.
23. 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.
24. 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.
25. There is an underground cave in the Dolomite Mountains in Italy where a Consortium of fruit growers store 40,000 tons of apples inside.