City Planets
City planets are awe-inspiring visions of civilization on an unprecedented scale. These colossal fictional cities stretch as far as the eye can see, covering entire planets with a tapestry of towering structures and bustling activity. Hoverlanes may ferry passengers and cargo between skyscrapers and archologies. Below may lay the dense slums of the underground sublevels, or a perpetual smog making the surface levels unhabitable. Even the near-orbital spaces above may have wonders to be found in the form of space elevators, planetary rings, and teleportation gates.

Synonyms: ecumenopolises |
Example Mythonyms: Capital Planet, Mons City Central |

Designing Fictional City Planets
Archetypes
Overview
Like with cyberpunk cities, the design of fictional ecumenopolises is a study in density across three dimensions. While a planet city may be divided into zones or districts (such as industrial zones, wealthy districts, trade districts, or slums), worldbuilders should also consider how such a city is divided within vertical space as well. Tall buildings may pierce the clouds and appear as islands in the mist. Below that, elaborate networks of skyway bridge systems may link together buildings at multiple levels. Elevated highways or railways may meander through the space below. The surface of the world may be held in a perpetual state of dim light for lack of penetrating sunlight. And then the underground: worldbuilders may want to consider a maze of underground tunnels, a secondary sub-city for poorer manual laborers and machines, or perhaps a series of sublevels connected to the surface by centralized vertical corridors.




Transportation
Transportation within an ecumenopolis is an area ripe for exploration. There may be trains, gondolas, or subways systems linking different areas within the city-planet. Hoverlanes of flying vehicles may crisscross the surface. Teleportation gates provide an additional potential fictional means of transport. Also consider the infrastructure necessary for these systems. Trains require train tracks or rail routes while road vehicles may require expansive highway systems.
As planet cities are often set in a future era, space travel is also a likely element also included. Travel to and from surface and off-world locations should be considered. City planets may feature spaceship ports, docks, and space shipyards.


The Skies Above
Ecumenopolises may feature additional elements present in their skies or in near orbit. While blimps, aerial platforms, and other floating structures or vehicles may be stationed above the cityscape, orbital rings, space elevators, planetary shields, and other orbital elements may also be present and visible from the surface.

Government
Consider how the government of a city planet is organized. Different sectors may have different representatives (if a form of democracy is used). There may be a large government center or palace located somewhere on the planet. Planet cities may also be the center of government for a galactic civilization.
Who are the policy-makers of this world?
Food
Feeding a population on a planet-wide scale is a massive endeavor made especially difficult if the majority of a planets’ surface is covered by massive buildings. Worldbuilders may solve this problem through the inclusion of large-scale hydroponic farms or vertical gardens. Of course, off-world farms are another option in settings with multiple planets.
If using off-world farms, consider what occurs when trade routes are interrupted or a blockade is put into place).
Power Systems
Powering a planet-sized cities may require unique solutions. Solar arrays, geothermal vents, fusion reactors, or future technologies may be required.

