Following the path, I reached the little rise from which I had first viewed the city and soon came to the spot where I had entered. Imagine my utter surprise when I saw no sign whatever of the opening. I was positive that I had not missed my way. I recognized the clumps of bushes and the forms of the rocks, but there was no dark hole, no aperture in the cliff. Then, as I drew near to the precipice, I made an astounding discovery. Closely fitted into the rock and so like it that it had escaped my attention, was an enormous stone door. How it was operated, whether it was hinged or slid or whether it was pivoted, I could not determine. But that it covered and concealed the entrance to the tunnel I was convinced. Why the people had left the tunnel open as though to clear the way for me, why they should have fitted a door to it, why they should ever use the tunnel which could bring them only to the death-dealing forest, were problems which I could not solve. At any rate there was nothing to be gained by staying there and I started back towards the city. Thinking to return by another route, I took a path that led towards the opposite mountain side and presently from ahead, I distinctly heard the sound of metal striking stone. Oddly enough my mind had been so filled with other matters that I had hardly wondered how these people cut or worked the hard stone. But now that my attention was attracted by the sound my curiosity was aroused and I hurried forward. What metal I wondered, did these people use? For metal I knew it must be from the ringing, clinking noise. Was I about to see hardened bronze tools in actual use or had these marvelous folk discovered the use of iron or steel? So astounding had been all my experiences, so paradoxical and incredible everything I had seen, that I was prepared for almost anything. I, or rather we, soon came to the verge of a deep pit wherein, laboring at great masses of white stone, were scores of workmen. Standing like skeletons among the blocks were derricks; hitched to sledge-like drags loaded with stone were teams of tapirs and on the farther side was a big outjutting ledge from which the stone was being quarried. Hurrying down the steep trail I reached the bottom of the pit to find every man flat on the ground.