Ecumenopolis (Borealis Universe)

An Ecumenopolis is a city which occupies the entire surface area of the planet it is on. The ecumenopolis is the staple of type III civilizations. With every known type-III civilization having at least one.

Design

These cities are typically built in layers, with the bottom layer on the surface of the planet. Each layer is usually over a kilometer apart from the layer above and below it. These cities typically have well over 100 layers each, with some of the largest ecumenopolises having over 150 layers.

These cities have trillions of construction drones milling along the vast support network, filling gin any cracks or fissures as they go.

Any oceans that exist on the surface of the planet are either polluted to the point of being useless or completely gone, used for drinking water by the vast populations. If the oceans are still there, they are buried under many layers, with a complex system of catwalks above them.

An ecumenopolis is usually devoid of any meaningful amount of plant life, so oxygen has to be synthesized artificially. Every ecumenopolis either creates oxygen via electrolysis of water or using cyanobacteria. The city goes through more oxygen a year than there was oxygen on earth in the 21st century.