The stone roof of this place was held up by huge stone pillars standing scattered about like groups of great rough-barked trees, many times bigger round than hogsheads.

Here and there in the roof, or the stone overhead, were immense black caverns which almost frightened him to gaze up at them, they were so vast and black.

And no light or sun or moon came down into that deep part of the earth: the light was from big fires, and they were fires of smithies burning all about him, sending up great flames and clouds of black smoke, which rose and floated upwards through those big black caverns in the roof.

Crowds of people were gathered around the smithies, all very busy heating metal and hammering on anvils like blacksmiths.
Never had he seen so many people, nor ever had he seen such busy men as these, rushing about here and there shouting and colliding with one another, bringing and carrying huge loads in baskets on their backs, and altogether the sight of them, and the racket and the smoke and dust, and the blazing fires, was almost too much for Martin; and for a moment or two he was tempted to turn and run back into the passage through which he had come.

But the strangeness of it all kept him there, and then he began to look more closely at the people, for these were the little men that live under the earth, and they were unlike anything he had seen on its surface.