Here’s what you’ll learn when you read this story:The discovery of more than 100 prehistoric structures in the Cova Dones cave in Spain makes it one of the most significant prehistoric underground sites in the world. Questions remain about the purpose of the underground structures in a cave already known for a wealth of finds. Prehistoric humans intentionally modified stalagmites in the Cova Dones cave in Spain, forming over 100 structures—known as speleofacts—as a result. The recent archaeological find becomes one of the most significant prehistoric underground discoveries in the world, according to the team behind the discovery. Located in Millares, Cova Dones may have just jumped to the forefront of prehistoric underground discussions, but answers may be hard to come by.