The whole region boils like an immense cauldron hung over subterranean fires.

If this is the case, its origin may well be attributed to subterranean fires.

I went on among the red reflections, which seemed like subterranean fires; I had a singular sensation of being in a very important dream.

In 2009 subterranean fires broke out after a hot summer: this was the first time they had affected the core area of the biosphere reserve.

The knowledge had lit a slow, subterranean fire in his imagination.

There are plenty of vapors ready to hand, and subterranean fires ready to issue forth.

This warmth, together with the red colour of the light, suggested that the upper cave was illuminated by subterranean fire.

It is caustic beneath from the smoke of subterranean fires.

But would the subterranean fires provoke any violent eruption?

Based on medieval belief that gnomes live in subterranean fire.