Dark Magic

The Tunnel-Mouth

Then the corridor ended in a prodigious open space which made us gasp involuntarily—a perfect inverted hemisphere, obviously deep underground; fully an hundred feet in diameter and fifty feet high, with low archways opening around all parts of the circumference but one, and that one yawning cavernously with a black arched aperture which broke the symmetry of the vault to a height of nearly fifteen feet. It was the entrance to the great abyss.

- H.P. Lovecraft

Bad Witches

...in layers.



Image from the Obscure Hollow blog.