The Culture hadn’t invented Orbitals like this, but it had taken them up with an enthusiasm nobody else had ever displayed, the Minds attracted both by the grandiosity of the concept – this was engineering on an epic scale, and even the skinniest full O had the surface area of twenty or thirty standard one-G planets – and by its sheer chronocyclic, material-frugal elegance; compared to planets, Orbitals represented a very matter-cheap way of providing generous amounts of pleasantly rural and even wild-looking living space, plus you could usually build your Orbitals from exactly the asteroidal debris you’d want to get rid of in a solar system anyway, to stop bits of it flying around and hitting your fancy new worlds.

Microrbitals were, as the name implied, much smaller versions of the same basic idea; they could be any diameter you wanted because the spin speed wasn’t rigidly linked to both the force experienced at their surface and their day/night cycle. You spun a microrbital at the appropriate rate to produce whatever apparent gravity you required, set it circumference-on to the sunlight, then put a suite of angled mirrors at its centre to reflect the light, rotating these independently to give you the desired light/dark periodicity.

The microrbital of Bokri was tiny; barely more than a thousand kilometres across. This was so small that the retaining side walls of sheet diamond which kept the atmosphere in would have met in the middle had the world been filled with a significantly denser atmosphere or spun much slower. As it was, the central mirrors were so close to the top of the walls that they rested on struts running along their inside edges so that the whole assemblage looked like the axle and spokes of a giant wheel.

The world was almost as long down its axis as it was wide and was conventionally arranged – by the relaxed, abundantly provisioned standards of a post-scarcity humanoid civilisation – with parkland, forests, lakes and aesthetically pleasing built-up areas and isolated grand architectural statements spread across its nearly three million square kilometres of interior surface.

The Gzilt had never entirely turned their backs on the ideas of both private ownership and money, though the latter had been demoted to being of mostly ceremonial value and both had been detached from what most people regarded as being the most important measure of a person’s worth; there had been enough of everything to go around everybody in the Gzilt civilisation for many millennia, and while a degree of self-interest and acquisitiveness was taken as being only natural, outright self-obsession and full-on greed were regarded as signs of weakness of character, if not a symptom of actual psychological damage.

The Bokri microrbital was joint-owned by a group of Secular Collectionary orders: institutionalised obsessive, only para-religious organisations, each devoted to one or other aspect of preservation.