Cavern

n.

1.

A large, deep, hollow place in the earth; a large cave.

Noun	1.	cavern - any large dark enclosed space; "his eyes were dark caverns"
	2.	cavern - a large cave or a large chamber in a cave
Verb	1.	cavern - hollow out as if making a cavern Synonyms: cavern out

abri, antre, bunker, burrow, cave, cove, dugout, foxhole, grot, grotto, hole, lair, sewer, subterrane, subterranean, subway, tunnel, warren