cave · cavern

A remote Iranian desert city, Ice Age-era caves in Germany and a stone wharf in Brazil built for arriving African slave ships are three new additions to UNESCO's list of World Heritage sites.

Tom was afraid to stay in the cave.

How many caves are there in this area?

The American Museum of Natural History’s “Creatures of Light” exhibit features jellyfish that glow green, anglerfish whose lantern-like bulbs dangle from their foreheads and luminous glowworms that hang mucus-like strands from cave ceilings to attract and ensnare their prey.

You wake up lying on the rocky floor of a dark cave. A little light filters down from above. You can just make out a couple of openings leading away from the cave. What do you do now?