He could have stood here for hours, admiring the view and still not exhausting all the wonders of this complex and brilliantly contrived simulation of the planet below. As it spread out into new and hostile environments, perhaps the human race felt an ever-increasing need to remember its origins. Of course, even in his own time every city had its parks as – usually feeble – reminders of Nature. The same impulse must be acting here, on a much grander scale. Central Park, Africa Tower!

'Let's go down,' said Indra. 'There's so much to see, and I don't come here as often as I'd like.'

Followed by the silent but ever-present Danil, who always seemed to know when he was needed but otherwise kept out of the way, they began a leisurely exploration of this oasis in space. Though walking was almost effortless in this low gravity, from time to time they took advantage of a small monorail, and stopped once for refreshments at a cafeґ, cunningly concealed in the trunk of a redwood that must have been at least a quarter of a kilometre tall.

There were very few other people about – their fellow passengers had long since disappeared into the landscape – so it was as if they had all this wonderland to themselves.

Everything was so beautifully maintained, presumably by armies of robots, that from time to time Poole was reminded of a visit he had made to Disney World as a small boy. But this was even better: there were no crowds, and indeed very little reminder of the human race and its artefacts.

They were admiring a superb collection of orchids, some of enormous size, when Poole had one of the biggest shocks of his life. As they walked past a typical small gardener's shed, the door opened – and the gardener emerged.