Beyond the barrier the cavern opened into a large chamber, whose floor sloped down no a central pool that stretched from wall to wall and separated them from the far wall. Everything was underlit by a luminescence that seemed to emanate from the milky water, making darker still the pockmarks of water-worn cavities in the walls. A natural bridge of stone stretched over the still waters. On the far side, three seams of opal cut diagonally through the sandstone wall. The opal gleamed with a thousand colors, bright beyond what might be expected from light reflected from the pool.