Cavern (noun)

1. A large underground chamber or series of chambers or passages, usually of natural origin.
2. A large, dark, or gloomy place.

Origin:

From middle english caverne, from old french caverne, from latin cava "hollow", from cavus "hollow".

Examples:

1. The cave explorers discovered a vast cavern deep beneath the surface.
2. The limestone caverns were formed by water erosion over thousands of years.
3. The cavern was lit by a faint light that filtered through a crack in the ceiling.
4. The cavern echoed with the sound of dripping water.
5. The cavern was full of stalactites and stalagmites.