3 ideas
Omale is the inner surface of a Dyson sphere around a central sun. Its surface area is so large that it holds multiple Earth-scale civilizations with room to spare. Humans live there alongside two alien species, the Hodgqins and the Chiles, all descended from populations transplanted by builders nobody remembers, and none of them knows its own origin or the purpose of the world they inhabit.
A world-book (livre-univers) is a work in which the invented world, not any character, is the true subject and the organizing principle of the narrative. Characters and plots serve as instruments for exploring the world's geography, ecology and societies. Their arcs matter less than what they reveal about how the world works.
Planetary exploration fiction runs out of blank space once the globe is mapped. A world with the surface area of millions of Earths makes the frontier effectively inexhaustible. Scale itself becomes the narrative engine: there is always another unknown civilization or landscape beyond the next range, so exploration never closes.