When we stopped at the water, Aryenis, who had been scanning the outlying hill ever since it first showed up, edged her camel out into the sand, and then gave a cry of joy, as round the shoulder of rock we saw the point where the outlying hill joined the main wall. “I was right. Look; there is the great arch,” she had cried. The outlier joined on to the high cliffs at a height of perhaps sixteen hundred or seventeen hundred feet. But at the junction swelled up the most peculiar natural formation I have ever seen. It was a giant arch of limestone, formed of strata bent by some primeval convulsion of the earth, and from which in the course of ages the central softer layers had been weathered away, leaving the hard outer ones as a true arch. One sees many cases where the strata run up into partial arches, leaving, as it were, the piers on either side and perhaps a small piece of the bow, but the central portion is always lacking, either snapped in the original disruption or weathered away later. Never before have I met a case of the whole fold remaining in arched form. Springing up from the crest of the hog-back to a height of some three hundred feet over a wide bow, it then curved in to join the great precipitous wall we had followed these last four days. And just above it in the cliff face were some dark shadows, which Aryenis was indicating as the caves of which she had told us. On looking with my glasses they proved to be, as she had said, unmistakable openings. “Can we climb up there?” she asked again impatiently. “They seem some height above the arch, and the sides of the lower hill are none too easy. But if we can get up anywhere, it will be at the point farthest out, which looks lower than the rest. We’ll call the others and ride over there.” We fetched Wrexham and Forsyth, and showed them the great arch and the caves above. “By Jove, what a quaint formation!” said Forsyth. “I’ve never seen a thing of that type on such a scale. I’ve seen tiny editions of it, but never anything approaching that size. It’ll take a bit of climbing, I should say, looking at it from here.” As we went out to the far end of the lower hill, we asked Aryenis if the caves were used by her people. “No. No one ever goes there now. They are very deep, and are supposed to have spirits in them, and people are afraid to go down into their darkness. They were once an old pagan temple, I think.” “How did you find your way into them, then?” I asked.