You continue down the main tunnel for several hundred yards, with nothing especially catching your eye. The moss has a soft texture under your fingers. At the end the tunnel makes a sharp left turn. As you round it, you are disappointed to find that the path splits, but both appear to have collapsed. The straight section caved in long ago, with moss growing on the rubble, but a large round stone looks to have recently rolled and blocks this offshoot passage. Small cracks at the base of the stone show the chipped away pieces are fresh, as the exposed surface hasn't changed color from exposure to air and moisture. You peer into the gaps to see if you can spot anything, but the openings are too narrow and the lights only show more stone and darkness beyond. You think, for a moment, that you hear a hissing sounds, but it's probably gasses escaping from a vent deeper in. Unable to venture any further, you return to the side passage you approached earlier.