We cannot yet explain the engineering principles used in the anomalous balancing and adjustment of the vast rock masses, though the function of the arch was clearly much relied on. The rooms we visited were wholly bare of all portable contents, a circumstance which sustained our belief in the city's deliberate desertion. The prime decorative feature was the almost universal system of mural sculpture, which tended to run in continuous horizontal bands three feet wide and arranged from floor to ceiling in alternation with bands of equal width given over to geometrical arabesques. There were exceptions to this rule of arrangement, but its preponderance was overwhelming. Often, however, a series of smooth car-touches containing oddly patterned groups of dots would be sunk along one of the arabesque bands.

The technique, we soon saw, was mature, accomplished, and aesthetically evolved to the highest degree of civilized mastery, though utterly alien in every detail to any known art tradition of the human race. In delicacy of execution no sculpture I have ever seen could approach it. The minutest details of elaborate vegetation, or of animal life, were rendered with astonishing vividness despite the bold scale of the carvings; whilst the conventional designs were marvels of skillful intricacy. The arabesques displayed a profound use of mathematical principles, and were made up of obscurely symmetrical curves and angles based on the quantity of five. The pictorial bands followed a highly formalized tradition, and involved a peculiar treatment of perspective, but had an artistic force that moved us profoundly, notwithstanding the intervening gulf of vast geologic periods. Their method of design hinged on a singular juxtaposition of the cross section with the two-dimensional silhouette, and embodied an analytical psychology beyond that of any known race of antiquity. It is useless to try to compare this art with any represented in our museums. Those who see our photographs will probably find its closest analogue in certain grotesque conceptions of the most daring futurists.

The arabesque tracery consisted altogether of depressed lines, whose depth on unweathered walls varied from one to two inches. When car-touches with dot groups appeared – evidently as inscriptions in some unknown and primordial language and alphabet – the depression of the smooth surface was perhaps an inch and a half, and of the dots perhaps a half inch more. The pictorial bands were in countersunk low relief, their background being depressed about two inches from the original wall surface. In some specimens marks of a former coloration could be detected, though for the most part the untold aeons had disintegrated and banished any pigments which may have been applied. The more one studied the marvelous technique, the more one admired the things. Beneath their strict conventionalization one could grasp the minute and accurate observation and graphic skill of the artists; and indeed, the very conventions themselves served to symbolize and accentuate the real essence or vital differentiation of every object delineated. We felt, too, that besides these recognizable excellences there were others lurking beyond the reach of our perceptions. Certain touches here and there gave vague hints of latent symbols and stimuli which another mental and emotional background, and a fuller or different sensory equipment, might have made of profound and poignant significance to us.

The subject matter of the sculptures obviously came from the life of the vanished epoch of their creation, and contained a large proportion of evident history. It is this abnormal historic-mindedness of the primal race – a chance circumstance operating, through coincidence, miraculously in our favor – which made the carvings so awesomely informative to us, and which caused us to place their photography and transcription above all other considerations. In certain rooms the dominant arrangement was varied by the presence of maps, astronomical charts, and other scientific designs of an enlarged scale – these things giving a naive and terrible corroboration to what we gathered from the pictorial friezes and dadoes. In hinting at what the whole revealed, I can only hope that my account will not arouse a curiosity greater than sane caution on the part of those who believe me at all. It would be tragic if any were to be allured to that realm of death and horror by the very warning meant to discourage them.

Interrupting these sculptured walls were high windows and massive twelve-foot doorways; both now and then retaining the petrified wooden planks – elaborately carved and polished – of the actual shutters and doors. All metal fixtures had long ago vanished, but some of the doors remained in place and had to be forced aside as we progressed from room to room. Window frames with odd transparent panes – mostly elliptical – survived here and there, though in no considerable quantity. There were also frequent niches of great magnitude, generally empty, but once in a while containing some bizarre object carved from green soapstone which was either broken or perhaps held too inferior to warrant removal. Other apertures were undoubtedly connected with bygone mechanical facilities – heating, lighting, and the like – of a sort suggested in many of the carvings. Ceilings tended to be plain, but had sometimes been inlaid with green soapstone or other tiles, mostly fallen now. Floors were also paved with such tiles, though plain stonework predominated.

As I have said, all furniture and other movables were absent; but the sculptures gave a clear idea of the strange devices which had once filled these tomblike, echoing rooms. Above the glacial sheet the floors were generally thick with detritus, litter, and debris, but farther down this condition decreased. In some of the lower chambers and corridors there was little more than gritty dust or ancient incrustations, while occasional areas had an uncanny air of newly swept immaculateness. Of course, where rifts or collapses had occurred, the lower levels were as littered as the upper ones. A central court – as in other structures we had seen from the air – saved the inner regions from total darkness; so that we seldom had to use our electric torches in the upper rooms except when studying sculptured details. Below the ice cap, however, the twilight deepened; and in many parts of the tangled ground level there was an approach to absolute blackness.

To form even a rudimentary idea of our thoughts and feelings as we penetrated this aeon-silent maze of unhuman masonry, one must correlate a hopelessly bewildering chaos of fugitive moods, memories, and impressions. The sheer appalling antiquity and lethal desolation of the place were enough to overwhelm almost any sensitive person, but added to these elements were the recent unexplained horror at the camp, and the revelations all too soon effected by the terrible mural sculptures around us. The moment we came upon a perfect section of carving, where no ambiguity of interpretation could exist, it took only a brief study to give us the hideous truth – a truth which it would be naive to claim Danforth and I had not independently suspected before, though we had carefully refrained from even hinting it to each other. There could now be no further merciful doubt about the nature of the beings which had built and inhabited this monstrous dead city millions of years ago, when man's ancestors were primitive archaic mammals, and vast dinosaurs roamed the tropical steppes of Europe and Asia .

We had previously clung to a desperate alternative and insisted – each to himself – that the omnipresence of the five-pointed motifs meant only some cultural or religious exaltation of the Archaean natural object which had so patently embodied the quality of five-pointedness; as the decorative motifs of Minoan Crete exalted the sacred bull, those of Egypt the scarabaeus, those of Rome the wolf and the eagle, and those of various savage tribes some chosen totem animal. But this lone refuge was now stripped from us, and we were forced to face definitely the reason-shaking realization which the reader of these pages has doubtless long ago anticipated. I can scarcely bear to write it down in black and white even now, but perhaps that will not be necessary.