a large cave or a large chamber in a cave
"The explorers descended into the cavern, where the ceiling was so high it seemed to touch the stars above them."
A large cave.
"The hikers descended into the cavern, where the darkness was so deep they could barely see their own hands."
hollow out as if making a cavern
"The stormy winds howled through the cave, sounding exactly as if someone had hollowed it out to create a cavern deep within the mountain."
To form a cavern or deep depression in.
"The relentless wind eroded the soft rock until it began to carve a shallow cavern along the cliffside."