After those interminable stairs, it was a strange luxury to walk once more on a horizontal surface. Directly ahead, the ground was indeed completely flat; to right and left, at the limits of the floodlit area, the rising curve could just be detected. They might have been walking along a very wide, shallow valley; it was quite impossible to believe that they were really crawling along the inside of a huge cylinder, and that beyond this little oasis of light the land rose up to meet—no, to become—the sky. Though they all felt a sense of confidence and subdued excitement, after a while the almost palpable silence of Rama began to weigh heavily upon them. Every footstep, every word, vanished instantly into the unreverberant void; after they had gone little more than half a kilometre Lt. Calvert could stand it no longer. Among his minor accomplishments was a talent now rare, though many thought not rare enough—the art of whistling. With or without encouragement he could reproduce the themes from most of the movies of the last two hundred years. He started appropriately with Heigh-ho, heigh-ho, ’tis off to work we go, found that he couldn’t stay down comfortably in the bass with Disney’s marching dwarfs, and switched quickly to River Kwai. Then he progressed, more or less chronologically, through half a dozen epics, culminating with the theme from Sid Krassman’s famous late-twentieth-century Napoleon. It was a good try, but it didn’t work, even as a morale-builder. Rama needed the grandeur of Bach or Beethoven or Sibelius or Tuan Sun, not the trivia of popular entertainment. Norton was on the point of suggesting that Joe save his breath for later exertions, when the young officer realized the inappropriateness of his efforts. Thereafter, apart from an occasional consultation with the ship, they marched on in silence. Rama had won this round.

On his initial traverse, Norton had allowed for one detour. Paris lay straight ahead, halfway between the foot of the stairway and the shore of the Cylindrical Sea, but only a kilometre to the right of their track was a very prominent, and rather mysterious, feature which had been christened the Straight Valley. It was a long groove or trench, forty metres deep and a hundred wide, with gently sloping sides; it had been provisionally identified as an irrigation ditch or canal. Like the stairway itself, it had two similar counterparts, equally spaced around the curve of Rama.

The three valleys were almost ten kilometres long, and stopped abruptly just before they reached the Sea—which was strange, if they were intended to carry water. And on the other side of the Sea the pattern was repeated: three more ten-kilometre trenches continued on to the South Polar region.

They reached the end of the Straight Valley after only fifteen minutes’ comfortable walking, and stood for a while staring thoughtfully into its depths. The perfectly smooth walls sloped down at an angle of sixty degrees; there were no steps or footholds. Filling the bottom was a sheet of flat, white material that looked very much like ice. A specimen could settle a good many arguments; Norton decided to get one.

With Calvert and Rodrigo acting as anchors and paying out a safety rope, he rappelled slowly down the steep incline. When he reached the bottom, he fully expected to find the familiar slippery feel of ice underfoot, but he was mistaken. The friction was too great; his footing was secure. This material was some kind of glass or transparent crystal; when he touched it with his fingertips, it was cold, hard and unyielding.

Turning his back to the searchlight and shielding his eyes from its glare, Norton tried to peer into the crystalline depths, as one may attempt to gaze through the ice of a frozen lake. But he could see nothing; even when he tried the concentrated beam of his own helmet-lamp he was no more successful. This stuff was translucent, but not transparent. If it was a frozen liquid, it had a melting point very much higher than water.

He tapped it gently with the hammer from his geology kit; the tool rebounded with a dull, unmusical “dunk”. He tapped harder, with no more result, and was about to exert his full strength when some impulse made him desist.

It seemed most unlikely that he could crack this material; but what if he did? He would be like a vandal, smashing some enormous plate-glass window. There would be a better opportunity later, and at least he had discovered valuable information. It now seemed more unlikely than ever that this was a canal; it was simply a peculiar trench that stopped and started abruptly, but led nowhere. And if at any time it had carried liquid, where were the stains, the encrustations of dried-up sediment that one would expect? Everything was bright and clean, as if the builders had left only yesterday…

Once again he was face to face with the fundamental mystery of Rama, and this time it was impossible to evade it. Commander Norton was a reasonably imaginative man, but he would never have reached his present position if he had been liable to the wilder flights of fancy. Yet now, for the first time, he had a sense—not exactly of foreboding, but of anticipation. Things were not what they seemed; there was something very, very odd about a place that was simultaneously brand new—and a million years old.

Very thoughtfully, he began to walk slowly along the length of the little valley, while his companions, still holding the rope that was attached to his waist, followed him along the rim. He did not expect to make any further discoveries, but he wanted to let his curious emotional state run its course. For something else was worrying him; and it had nothing to do with the inexplicable newness of Rama.

He had walked no more than a dozen metres when it hit him like a thunderbolt.

He knew this place. He had been here before. Even on Earth, or some familiar planet, that experience is disquieting, though it is not particularly rare. Most men have known it at some time or other, and usually they dismiss it as the memory of a forgotten photograph, a pure coincidence—or, if they are mystically inclined, some form of telepathy from another mind, or even a flashback from their own future.

But to recognize a spot which no other human being can possibly have seen—that is quite shocking. For several seconds, Commander Norton stood rooted to the smooth crystalline surface on which he had been walking, trying to straighten out his emotions. His well-ordered universe had been turned upside down, and he had a dizzying glimpse of those mysteries at the edge of existence which he had successfully ignored for most of his life.

Then, to his immense relief, common sense came to the rescue. The disturbing sensation of déjà-vu faded out, to be replaced by a real and identifiable memory from his youth.

It was true—he had once stood between such steeply sloping walls, watching them drive into the distance until they seemed to converge at a point indefinitely far ahead. But they had been covered with neatly trimmed grass; and underfoot had been broken stone, not smooth crystal.

It had happened thirty years ago, during a summer vacation in England. Largely because of another student (he could remember her face—but he had forgotten her name) he had taken a course of industrial archaeology, then very popular among science and engineering graduates. They had explored abandoned coal-mines and cotton mills, climbed over ruined blast-furnaces and steam engines, goggled unbelievingly at primitive (and still dangerous) nuclear reactors, and driven priceless turbine-powered antiques along restored motor roads.

Not everything that they saw was genuine; much had been lost during the centuries, for men seldom bother to preserve the commonplace articles of everyday life. But where it was necessary to make copies, they had been reconstructed with loving care.