The doors opened silently, and as Poole stepped out he again felt the slight disorientation he had noticed on entering the elevator lounge. This time, however, he knew what it meant: he was moving through the transition zone where the inertial field overlapped with gravity – at this level, equal to the Moon's.

Indra and Danil followed him, walking carefully now at a third of their customary weight, as they went forward to meet the next of the day's wonders.

Though the view of the receding Earth had been awesome, even for an astronaut, there was nothing unexpected or surprising about it. But who would have imagined a gigantic chamber, apparently occupying the entire width of the Tower, so that the far wall was more than five kilometres away? Perhaps by this time there were larger enclosed volumes on the Moon and Mars, but this must surely be one of the largest in space itself.

They were standing on a viewing platform, fifty metres up on the outer wall, looking across an astonishingly varied panorama. Obviously, an attempt had been made to reproduce a whole range of terrestrial biomes. Immediately beneath them was a group of slender trees which Poole could not at first identify: then he realized that they were oaks, adapted to one-sixth of their normal gravity. What, he wondered, would palm frees look like here? Giant reeds, probably...

In the middle-distance there was a small lake, fed by a river that meandered across a grassy plain, then disappeared into something that looked like a single gigantic banyan tree. What was the source of the water? Poole had become aware of a faint drumming sound, and as he swept his gaze along the gently curving wall, he discovered a miniature Niagara, with a perfect rainbow hovering in the spray above it.