You choose to enter the tunnel right in front of you. It is dark, but you take cautious steps into the passage.
About five minutes later, you turn a corner and find yourself blinded by light! You cover your eyes and wait for your eyes to adjust, and once they do you see a room full of crystals! There were so many different crystals, a few were VERY beautiful, and there were crystals providing light to the cave from the ceiling and walls.