The whole cave -- the walls, the riverbed, the ceiling, even the floor beneath their hooves -- seemed to be made out of thousands upon thousands of small pillars of dark grey stone, each about a hoof or two in diameter, and none of them quite even with their neighbor. Almost as if somepony built this place out of foal's toys... or stacks of paving stones. It made for a striking effect as the light from above reflected off the water below and sent shadows rippling across the zig-zagging surface.