Placing the man’s helmet over his dead, staring face, I straightened up and stepped back through the unseen doorway to the entrance hall of the great enclosure. All my curiosity about the strange edifice now returned, and I racked my brain with speculations regarding its material, origin, and purpose. That the hands of men had reared it I could not for a moment believe. Our ships first reached Venus only 72 years ago, and the only human beings on the planet have been those at Terra Nova. Nor does human knowledge include any perfectly transparent, non-refractive solid such as the substance of this building. Prehistoric human invasions of Venus can be pretty well ruled out, so that one must turn to the idea of native construction. Did a forgotten race of highly evolved beings precede the man-lizards as masters of Venus? Despite their elaborately built cities, it seemed hard to credit the pseudo-reptiles with anything of this kind. There must have been another race aeons ago, of which this is perhaps the last relique. Or will other ruins of kindred origin be found by future expeditions? The purpose of such a structure passes all conjecture — but its strange and seemingly non-practical material suggests a religious use.
Realising my inability to solve these problems, I decided that all I could do was to explore the invisible structure itself. That various rooms and corridors extended over the seemingly unbroken plain of mud I felt convinced; and I believed that a knowledge of their plan might lead to something significant. So, feeling my way back through the doorway and edging past the body, I began to advance along the corridor toward those interior regions whence the dead man had presumably come. Later on I would investigate the hallway I had left.
Groping like a blind man despite the misty sunlight, I moved slowly onward. Soon the corridor turned sharply and began to spiral in toward the centre in ever-diminishing curves. Now and then my touch would reveal a doorless intersecting passage, and I several times encountered junctions with two, three, or four diverging avenues. In these latter cases I always followed the inmost route, which seemed to form a continuation of the one I had been traversing. There would be plenty of time to examine the branches after I had reached and returned from the main regions. I can scarcely describe the strangeness of the experience — threading the unseen ways of an invisible structure reared by forgotten hands on an alien planet!
At last, still stumbling and groping, I felt the corridor end in a sizeable open space. Fumbling about, I found I was in a circular chamber about ten feet across; and from the position of the dead man against certain distant forest landmarks I judged that this chamber lay at or near the centre of the edifice. Out of it opened five corridors besides the one through which I had entered, but I kept the latter in mind by sighting very carefully past the body to a particular tree on the horizon as I stood just within the entrance.
There was nothing in this room to distinguish it — merely the floor of thin mud which was everywhere present. Wondering whether this part of the building had any roof, I repeated my experiment with an upward-flung handful of mud, and found at once that no covering existed. If there had ever been one, it must have fallen long ago, for not a trace of debris or scattered blocks ever halted my feet. As I reflected, it struck me as distinctly odd that this apparently primordial structure should be so devoid of tumbling masonry, gaps in the walls, and other common attributes of dilapidation.
What was it? What had it ever been? Of what was it made? Why was there no evidence of separate blocks in the glassy, bafflingly homogeneous walls? Why were there no traces of doors, either interior or exterior? I knew only that I was in a round, roofless, doorless edifice of some hard, smooth, perfectly transparent, non-refractive, and non-reflective material, an hundred yards in diameter, with many corridors, and with a small circular room at the centre. More than this I could never learn from a direct investigation.
I now observed that the sun was sinking very low in the west — a golden-ruddy disc floating in a pool of scarlet and orange above the mist-clouded trees of the horizon. Plainly, I would have to hurry if I expected to choose a sleeping-spot on dry ground before dark. I had long before decided to camp for the night on the firm, mossy rim of the plateau near the crest whence I had first spied the shining crystal, trusting to my usual luck to save me from an attack by the man-lizards. It has always been my contention that we ought to travel in parties of two or more, so that someone can be on guard during sleeping hours, but the really small number of night attacks makes the Company careless about such things. Those scaly wretches seem to have difficulty in seeing at night, even with curious glow-torches.