Drenched in the crimson light of the sun behind us, it was a crimson world that lay beneath us, a lurid world whose mountains, plains and valleys were all of the same blood-like hue as the light that fell upon them, whose very lakes and rivers gave back to the sky the scarlet tinge that pervaded all things here. And as our cruiser swept lower we saw, too, that the redness of the planet beneath was no mere illusion of the crimson sunlight but inherent in itself, since all of the vegetation below, grassy plains and tangled shrubs and stunted, unfamiliar trees, were of that same red tinge that was the color-keynote of this world. Strange and weird as it appeared, though, there seemed no sign of life on the broad plains and barren hills beneath us, and abruptly Sarto Sen headed the ship across the planet's face, speeding low over its surface while we scanned intently the panorama that unrolled beneath us. For minutes our straining scrutiny was unrewarded; and then, far ahead, a colossal shape loomed vaguely through the dusky crimson light, taking form, as we sped on toward it, as a tremendous, soaring tower. And involuntarily we gasped as our eyes took in the hugeness of its dimensions. It consisted of four slender black columns, each less than fifty feet in thickness, which rose from the ground at points a half-mile separated, four mighty pillars which slanted up into the crimson sunlight for fully ten thousand feet, meeting and merging at that distance above the ground and combining to support a circular platform two hundred feet in diameter. Our ship was hovering a few thousand feet above this platform, and on it we could see the shapes of what appeared to be machines, and other shapes that moved about them, though whether these last were human or not could not be distinguished from our height. And then, as my gaze fell toward the mighty tower's base, my cry brought the eyes of the others to follow my pointing finger. For gathered beneath and around the tower and extending away into the surrounding country were the massed buildings of a city. Low and flat-roofed and utterly strange in appearance were those buildings, and the narrow streets that pierced their huddled masses were all of the same smooth blackness as the tower itself--black, deep black, the roofs and streets and walls, laced with crimson parks and gardens that lay against their blackness like splashes of blood. And looming over all, its four tremendous columns rearing themselves above the streets and roofs and gardens like the limbs of a bestriding giant, the mighty tower soared into the crimson sunlight. Sarto Sen flung an arm down toward the tower's platform, beneath us, and toward the shapes that moved on that platform. "Inhabited!" he cried. "You see? And that means that Alto's change in course was--"