subterranean room

Within the subterranean room of the cavern of machinery, Mary Atwood and I sat on the couch.

She tells me that you have left Mr. Fentolin and the others in the subterranean room of the Tower.

A tiny, almost subterranean room was serving him for dwelling and workshop.

In the tiny, subterranean room (not much larger than a cell) a stick of incense burned.

Edith stood in the door of the subterranean room, regarding me smilingly, but with eyes full of sympathetic distress.