"洞" (dòng) in Chinese is translated to "cave" in Engpsh. The word comes from Old Engpsh "caf" and Old Norse "gufa", both meaning "a hollow place in the ground".
Examples:
The cave was dark and damp. (这个洞穴黑暗潮湿。)
The explorers found an ancient painting in the cave. (探险家们在洞穴里发现了一幅古代画。)
The bats pve in the cave. (蝙蝠住在洞穴里。)