When the city decided to rid itself of humans, it finally came into its own.

Its self-construction algorithms could soar higher and finer into the blue skies. Straight lines and clean, feature-free surfaces could dispense with fussy curves and poxing windows. Highways six storeys tall never saw congestion, and pedestrians need never cross paths with motor vehicles; there were none of either.

Nor would pedestrians stray from the paved paths. Grass was mown and kept off, without cluttering signs to enforce things. Ball games were not allowed, and not played. Litter was absent and the river flowed clean and pure – the pink hue from the inhabitants died away, given time.

Wildlife and birdsong filled the parks; the litter bins never overflowed and dog dirt was never seen.