A cave is "a natural opening in the ground extending beyond the zone of light and large enough to permit the entry of man," according to the U.S. Geological Survey. Caves can range in size from single rooms to large formations with winding passageways that extend for miles. Caves typically form in types of rock, such as limestone, that dissolve in water. It can take tens of thousands to hundreds of thousands of years for caves to form. The study of caves is called speleology, and the exploration of caves is called spelunking. Caves are famous of their dripstone features called speleothems, the most well-known of which are stalactites and stalagmites. Many of the strange creatures found in caves have adapted to live in near or total darkness — some are blind to visible light. See cave pictures and read about the latest cave discoveries and speleological research below.
Malham Cave in the Negev Desert is the longest salt cave in the world, measuring more than 6 miles (10 kilometers) in total length, researchers say.
The Neanderthals and Denisovans — both relatives of modern humans — were roommates, literally, for thousands of years in a remote Siberian cave, two new studies find.
Government officials and rescue workers in Thailand are mobilizing to save a group of young boys and their soccer coach, stranded in a cave underground.
The boys who survived for 9 days in a flooded cave in Thailand will now have to go through a risky crash course in cave diving in order to make their way out.
The youth soccer team and its coach in Thailand that had gone missing in the Tham Luang caves for more than a week have been found.
From ice age animals to Maya altars, the world's biggest underwater cave system has big potential for discoveries.
Human cannibals likely took a big bite out of their fellow humans about 10,000 years ago, according to a study that examined prehistoric bones with scratch and bite marks on them.
A newfound, 400,000-year-old hominin skull has a few telltale features suggesting that it's more of a Neanderthal than a Homo sapiens relation, a new study finds.