Streaks of glowing lichen run along the striated walls, lending a little light, enough to see the little bits of gravel and dust on the floor. Up above, the ceiling is dark, and rather high. Within the quiet alcove, on the center of the floor, is a pyramid-shaped crystal, a prism, through which the light of the bright lichen passes, breaking apart and defracting to various colors, catching some of the wall lichen and coloring them. The prism slowly, quietly rotates, floating just a wee bit above the floor, so that the color does not remain on the same set of lichen, but is shared by all at one time or other. In the course of the day, the pyramidal prism rotates one full rotation. The rest of the underground cavern is to the north, beyond the huge vaulted opening.