A cave or cavern is a natural void in the ground,Whitney, W. D. (1889). "Cave, n.1." def. 1. The Century dictionary: An encyclopedic lexicon of the English language (Vol. 1, p. 871). New York: The Century Co."Cave" Oxford English Dictionary Second Edition on CD-ROM (v. 4.0) © Oxford University Press 2009 specifically a space large enough for a human to enter. Caves often form by the weathering of rock and often extend deeply underground. The word cave can also refer to much smaller openings such as sea caves, rock shelters, and grottos, though strictly speaking a cave is exogene, meaning it is deeper than its opening is wide, and a rock shelter is endogene.
List of caves in Iran