A cave or cavern is a natural underground space large enough for a human to enter. The term applies to natural cavities some part of which is in total darkness. The word cave also refers to smaller spaces like rock shelters, sea caves, and grottos.
Speleology is the science of exploration and study of all aspects of caves and the environment which surrounds the caves.
For more, see List of longest caves.
- Mammoth Cave, Kentucky, USA
- Jewel Cave, South Dakota, USA
- Optymistychna Cave, Ukraine
- Wind Cave, South Dakota, USA
- Sistema Sac Actun, Mexico
Stalactites and stalagmites are types of mineral deposits found in caves that accrue through the processes of solution and deposition. Stalactites hang downwards from the ceiling of caves, whereas stalagmites rise upwards from the floor of a cave.