Down to the left...
The cavern to your left slopes downward at a slight angle. As you walk carefully among the columns of rock, you can see that the rock formations are very unusual - the geology seems to have changed suddenly in several places.
As you continue forward, the slope gets slightly steeper. You go on, and suddenly find yourself at a wall that comes only halfway between the floor and the ceiling. Down below, you can hear something pulverizing the rocks and walls.
As the cleric's holy symbol's light floods over the wall, a sudden rainbow of light crosses your eyes, and you are forced to cover them.
You manage to regain your sight, and look below again. Huge beasts, made out of what seems to be rock and stone, are slowly mowing through the rocky wall. As they do, veins of various gems - ruby, sapphire, topaz, emerald, even a few diamond - come into view, and the precious gems tumble in chunks onto the floor. A few scattered Thri-Kreens walk about, gathering up the chunks and placing them in large piles, each one consisting of a different color.
Some sit on the floor near a purplish pile, splitting what appear to be geodes in half and tossing them on the pile.
None of the 'Kreens seem to notice your presence, nor do any of the odd, moving mounds of stone and rock.
As you look about, you also notice two tunnels, one on either side of the cavern you are in from your present location (right and left). Both seem to go downward, and the one of the left exhibits what look like the beginnings of a staircase, but it continues on into the darkness beyond the tunnel entrance.
Thus - below you there is a great cavern, filled with rocky creatures and Thri-Kreen, and many piles of gems of various sorts. To your right and left are tunnels, both of which appear to head down, the left one appearing to have a staircase.