[[quoteright:330:[[TransformersWarForCybertron http://static.tvtropes.org/pmwiki/pub/images/cybertron_1153.jpg]]]]
[[caption-width-right:330:I guess they grow their food on Energon Farms?]]

->''"Coruscant… the capital of the Republic… the entire planet is one big city."''
-->-- '''[[CaptainObvious Ric Olié]]''', ''Franchise/StarWars: Film/ThePhantomMenace''

A City Planet is a {{subtrope}} of SingleBiomePlanet and MegaCity, in which said biome ''is'' said city. In other words, this is what happens when someone takes {{Planetville}} a little too literally: there is only one "city" on the planet, and it covers the ''entire'' planet.

Sometimes referred to as a planet city, world city (though "world city" has also been used to mean other things), completely urbanized world, omniopolis / omnopolis, or [[http://en.wikipedia.org/wiki/Ecumenopolis ecumenopolis]]. While most examples are recent, the concept dates as far back as the nineteenth century work of [[http://en.wikipedia.org/wiki/Thomas_Lake_Harris Thomas Lake Harris]], and the term "City Planet" dates at least as far back as the first draft of the script for ''Franchise/StarWars: Film/ANewHope''.

This trope occurs as the apparent result of a civilization, presumably over centuries of expansion, converting the entire surface of a world into one vast city. To be sure, many City Planets are divided into "administrative sectors" or other such local government institutions, but for all practical purposes, it's all the same city. Generally, this trope implies that for all practical purposes, the only biome of importance on the planet is urban jungle. Taken to an extreme, it may be implied the locals even paved over volcanoes and oceans in the process of creating the City Planet.

In works not all the way to the less realistic end of MohsScaleOfScienceFictionHardness or the SlidingScaleOfRealisticVersusFantastic, such a world can present a Mega City-sized ball of FridgeLogic. Perhaps most importantly, what do people eat if there is no farmland? Often it's simply {{handwave}}d, but other times it's revealed that:
* The local StarfishAliens don't need food as we might understand it.
* Food and other supplies have to be imported from elsewhere at great expense.
* Massive greenhouses for crops and battery farms for livestock.

Because SciFiWritersHaveNoSenseOfScale, City Planets tend to have implausibly low populations. An Earth-sized planet with the population density of [[BigApplesauce Manhattan]] would have 4 trillion people, while a world [[SkyscraperCity covered with miles-high buildings]] would be far denser than that. But it's rare to see a planet with more than a trillion inhabitants. However, this assumes a near-universal population density throughout the planet and no large, minimally populated areas of automated processing (as the third option mentioned above might imply).

Alternately, the trope will be subverted, introducing the audience to a seemingly endless city, and only later revealing that there are, in fact, vast areas of truly rural or wilderness areas remaining, the locals just don't like to talk about it.

Another {{subversion}} can be that the city, despite covering an entire world, is no bigger than an "ordinary" city - because [[BabyPlanet the planet is so small]]. In the past, such stories seemed more realistic than they do today; however, many serious hard - SciFi tales involve colonizing an asteroid or a city - sized space station. In recent decades, computer image manipulation technology has resulted in these occasionally showing up in video games or humorous images.

Finally, in some settings, a city occupies not a planet, but an entire plane of existence, a layer of a LayeredWorld, or other planet - like... thing.


!!"Traditional" Examples:

[[folder:Anime & Manga]]
* Creator/TsutomuNihei's ''Manga/{{Blame}}'' is set in a City ''DysonSphere'' [[UpToEleven that is implied to have long since consumed the solar system with its sheer enormity]].
* In ''Anime/TransformersCybertron'', in addition to the title planet, over thousands of years of relentless construction, Gigantion has become several massive layers of city surrounding an Earth-like inner planet.
* Pestako from ''TheFiveStarStories''. A small, pluto-like planetoid with no natural atmosphere that was originally used for mining, the planet has glittering bands of light stretching across its surface that are actually highways so big you can see them from space.

[[folder:Comic Books]]
* From DCComics JackKirby's ''FourthWorld'' series, Apokolips.
* The concept is taken even further with The Hub in ''TransformersGeneration2'' a vast physically connected network of Cybertron-type worlds that serves as the centre for power of the Cybertronian Empire.
* The eponymous planet in Creator/AlejandroJodorowsky's ''ComicBook/{{Megalex}}''.
* British 1980's science fiction comic ''Starblazer''.
** Issue 28 "Last Man on Earth". The Wheel was the fifth planet of Alpha Centauri. It was a planet-city ruled by a dictatorial {{AI}} computer.
** Issue 29 "The Moonstealers". The planet Joaphat is covered entirely by a gigantic city with no areas of countryside.
** Issue 59 "Starseeker Squad". The planet Bessel has an Earth city/colony that covers the entire planet.
** Issue 64 "The Exterminator". Vanderdecken is a vast, ancient city-planet. Although this mysterious world is millions of years old, everything on it is in perfect operating condition.
** Issue 208 "Planet of the Dead". The planet Vegas Prime is entirely covered in all manner of vice dens.

* ''Franchise/StarWars'' has Coruscant, the capital of the Galactic Republic. Other, lesser-known planets and moons also fit the bill, such as Nar Shaddaa.
** In ''[[Franchise/StarWarsExpandedUniverse The Hutt Gambit]]'', Han Solo notes that the uppermost levels of [[WretchedHive Nar Shaddaa]] look like the lowermost levels of {{C|rystalSpiresAndTogas}}oruscant. He promptly resolves NEVER to visit the lowermost levels of Nar Shaddaa.
** It is interesting to note that Coruscant escapes some of the population questions specifically because it is depicted as having extensive areas dedicated to purposes other than habitation. In ''AttackOfTheClones'' and ''RevengeOfTheSith'' industrial zones and landing areas for spaceships more than a kilometer in length are shown. ''Everything'' is bigger on Coruscant! Even with vast areas that are unpopulated, ExpandedUniverse sources and one of the movie novelizations peg Coruscant's population at upward of 1 trillion permanent residents plus billions of transients. As a result, the planet has to import vast amounts of food from elsewhere.
* In ''Film/StarTrekFirstContact'', Earth has become this under Borg rule in an alternate timeline. Oddly enough the population consists of only 9 billion Borg even though the planet's entire surface seems to have been completely urbanized and technified. The planet might be [[EternalEngine one huge automated factory.]]
* In the Film/SuperMarioBros [[TheMovie Movie]], Koopa's globe of the [[HumanAliens dinosaur-ruled]] [[AlternateHistory parallel Earth]] includes a stylized depiction of a country-sized city as an island in a [[SingleBiomePlanet worldwide desert]] ([[OneWorldOrder which he counts as under his rule]]). As far as logistics, there's a severe shortage of food, clean air, and water, but it's largely blamed on Koopa's 20-year regime (and is the driving force behind his planned conquest of ''our'' Earth).

* In Creator/IsaacAsimov's novels:
** Trantor, capital of the Galactic Empire, is apparently completely covered by urban areas by the time of the ''{{Foundation}}'' series. Until it's [[PlanetLooters sacked and looted]] into an agrarian world once the Empire falls.
*** In the prequel ''Prelude to Foundation'', it is revealed that the planet is divided into approximately 800 [[DomedHometown domed cities]], each with their own subcultures, with some open space in-between used for transportation, communication, cooling towers, etc. Trantor consumes most of the exports from a number of neighboring systems. (''Prelude'' can be considered Asimov's attempt to [[{{Reconstruction}} reconstruct]] this trope.)
*** In the ''Foundation'' series Asimov stated that he was drawing a direct historical parallel from Gibbon's ''Decline and Fall of the Roman Empire''. Ancient Rome was then the world's largest metropolis, with a population of over a million people, something which would not be matched again until 19th Century London. Rome was so densely populated that it could not sustain itself off of local agriculture and food was shipped constantly from North Africa to supply the city. Trantor likewise is dependent on imports of food from other planets, a point which becomes historically important in the fall of Trantor as the capital of the Galactic Empire. The final claimants to the title of Emperor are eventually forced to move to another planet, much as the Roman government relocated to Ravenna during the transition to the Dark Ages.
** In his robot novels, Earth has become a planet of underground or domed "[[CapitalLettersAreMagic Cities]]". There's still wilderness outside, but very few people ever go there, so from the protagonists' point of view, they live on a CityPlanet. In fact, airplanes no longer have windows because most people are agoraphobic and would have panic attacks during flights if they could see outside of the plane. All of this is contrasted by the Spacers, whose worlds have a very low population density and as a result they prefer to live on estates with a lot of open space. This presents a real challenge to the agoraphobic protagonist Elijah when he visits the Spacer Worlds.
*** Incidentally, Asimov himself was a claustrophile (i.e. he liked small, enclosed spaces)--he wasn't exactly an agoraphobe--and hated flying.
* AndreNorton's ''Uncharted Stars'' has a planet completely covered by city.
* ''Literature/BillTheGalacticHero'' by Creator/HarryHarrison features a world-covering city, Helior. While visiting, Bill suffers a grievous mishap: the map of the city chained to his arm is stolen leaving him one of the desperate Unplanned, with no hope of ever discovering where he is or where he needs to be.
** It's worse than that. Losing a map is a crime on Helior. If you're caught without one, you're arrested.
** It's pointed out that Helior imports all its food from agricultural planets in exchange for fecal waste to use as fertilizer. Apparently, they use the same transport ships for both. Bill also finds and nearly joins the organization responsible for waste disposal and recycling. They're desperately trying to find ways of re-using the stuff people throw away or, at least, prevent people from throwing away things, like plastic coffee cups that turn into music discs when they're empty.
* In the works of Creator/SheriSTepper:
** In ''Beauty'', the Earth has had all its wilderness wiped out, followed by any and all crop growing facilities.
** And in ''Shadow's End'', the governing planet of an entire solar system is a City Planet.
* In ''Ecumenopolis'', author, architect, and urban planner Constantinos A. Doxiadis [[http://www.doxiadis.org/files/pdf/City%20of%20the%20Future.pdf suggests the Earth's fate is to a mild version of this, with rural and wilderness areas reduced to islands between the interconnecting "bridges" and "nodes" of a single city]].
* ''[[OrsonScottCard The Worthing Saga]]'' shows in passing how one of these came to be. The short story "Skipping Stones" begins on a world that's heavily developed, but is still famous for its wildlife, particularly its "whiplash trees" that bend all the way to the ground in windstorms. As the skyscrapers go up, the trees go extinct, and eventually all the planet has become the "Capitol" that is the focus of later stories.
* In Emma Clayton's ''The Roar'', "The Upper Half of the World".
* From Creator/DanSimmons' ''Literature/HyperionCantos'', Tau Ceti Center and Renaissance Vector. Simmons at first [[JustifiedTrope explains away]] the food problem by means of the interstellar PortalNetwork (the farcasters) that make the transport of food from offworld a trivial matter (this same technology, after all, allows you to have a ''single house'' on ''twenty-plus worlds''--if you're rich). After the network disappears, Tau Ceti Center collapses and becomes entirely deserted, while Renaissance Vector is able to hold on due to the existence of another planet with good agricultural land, Renaissance Minor, in the same star system.
* The Franchise/StarWarsExpandedUniverse includes at least eighteen of these planets. Each has populations in the trillions and requires several nearby planets to support it. A complete list can be found [[http://starwars.wikia.com/wiki/Ecumenopolis here.]]
* The titular planet of Riesel in ''[[Literature/RieselTalesTwoHunters Riesel Tales: Two Hunters]]'' is an ecumenopolis with not only a miles-high skyline, but mountain-sized masses of detached cityscape that float within the polluted skies. However, the planet's glory days are long gone. Most of the cityscape is dirty and rusting, and vast swaths have been outright abandoned; though there are a few good expanses of up-to-date, crowded cityscape. [[WretchedHive Crime is rampant]], and the planet itself is run by a powerful [[TheMafia mafia]]. While it has a population of twelve trillion, this is considered ''anemic'' in comparison to other urban worlds in the galaxy, which tend to have at least [[UpToEleven ten times]] as many people. A more comprehensive description can be found in the Riesel Tales [[http://rieseluniverse.wikia.com/wiki/Riesel wiki.]]
* In Creator/JackWilliamson's "Literature/TheCosmicExpress" (1931), the Earth of 2432 is well on its way to becoming one of these. Much of the world is covered by cities, often domed cities, with most of the remaining space being used for farms, parks, and resorts. Wild Nature is gone, which is one of the principal complaints of main characters Eric and Nada.
* In the ''Literature/ParadoxTrilogy'', aeons have a flocking instinct which makes them prefer living with a high population density, thus planets colonized by them tend to be city planets.

[[folder:Live Action TV]]
* ''Series/DoctorWho'' features a library planet in "Silence in the Library" / "Forest of the Dead", which is deserted due to a colony of [[LivingShadow Vashta Nerada]].
** San Helios from "Planet of the Dead" was once one, before The Swarm reduced everything on that world to sand.
* The American ''SpacePatrol'' had Terra, the man-made planet (although that's more of a "Space Canberra")

* The alien warworld in ''Pinball/{{Firepower}}'' is completely covered with assorted metal structures.

[[folder:Tabletop Games]]
* A specific example from ''TabletopGame/{{Warhammer 40000}}'' is [[EarthIsTheCenterOfTheUniverse Holy Terra]], its oceans drained away and its surface completely overgrown with cathedrals and administrative buildings (the Imperial Palace itself covers most of Europe, while the Astronomican is inside a hollowed-out Mount Everest). The [[EternalEngine Forge Worlds]] of the [[MachineWorship Adeptus Mechanicus]] are planet-sized industrial sectors, while Hive Worlds are only partial examples, consisting of [[MegaCity enormous arcologies]] dotting a vast {{polluted wasteland}}. Finally, Necron Tomb Worlds are covered in eons-old alien ruins, beneath which deathless metal warriors slumber in stasis... at least until interlopers wake them up.
** It's explicitly mentioned there that all these specialized worlds do import their food from nearby agri-worlds. Well... probably not the Tomb Worlds.
* ''TabletopGame/DyingEarth'' RPG supplement ''Turjan's Tome of Beauty and Horror''. The planet of Merchdilan is entirely devoted to business/commerce and entirely covered by city.
* In ''Dragonstar'', Draconis Prime.
* ''TabletopGame/MagicTheGathering'' has Ravnica, a rare fantasy example. To solve the food issue, one of Ravnica's ten Guilds is devoted to spreading and preserving growth on every available inch of the city. Another is devoted almost entirely to various forms of compost and recycling, including necromancy. Yet another is constantly developing new organisms that will thrive in the endless urban sprawl.
* ''TabletopGame/SLAIndustries''. All Industrial Worlds, including Mort, have their land surface (and most of their seas) completely covered with industrial production facilities and cities.

[[folder:Video Games]]
* ''Emperor of the TabletopGame/FadingSuns'' features the planets of Byzantium Secundus and Leaguehiem. In terms of game rules new cities can't be built on these worlds (not that the Imperial Guard on Byzantium II would allow any units outside the embassies) as every hex is already covered with cities.
* ''VideoGame/TotalAnnihilation'': Subverted, Core Prime is a giant computer containing the conscience of the whole population and the entire Core culture.
* From ''VideoGame/{{Freelancer}}'', the planets Manhattan, New Berlin, New Tokyo and New London.
* ''VideoGame/{{Starcraft}}'' also features several.
* From ''VideoGame/{{Meteos}}'', the [[WorldShapes oddly-shaped]] world of Grannest.
* Zerard from ''RogueGalaxy''.
* Sunder from ''VideoGame/{{Anachronox}}''.
* Parum from ''PhantasyStarUniverse''. Though large sections are given over to nature reserves, the majority of the planet is urbanized.
* Earth in ''VideoGame/StarOceanTillTheEndOfTime''. Cities still appear to have individual regional styles, like New York, but together seem to cover the whole planet.
* Feros from ''Franchise/MassEffect'' is home to a sprawling ruin that covers at least two-thirds of the planet's surface. The remaining third is presumably that of the planet's ocean, though because of the dust and debris thrown about in the storms that plague the ground level, it's apparently hard to tell.
* New Kroy (invert the letters in ''Kroy'', by the way, [[PunnyName and see what you get]]) from ''VideoGame/{{Fury}}''.
* VideoGame/{{Z}}: One of the five planets in the game is of this type.
* Taris in Star Wars: ''VideoGame/KnightsOfTheOldRepublic''


* ''Webcomic/IrregularWebcomic'' spends a number of Star Wars strips deconstructing the idea, such as [[http://www.irregularwebcomic.net/386.html food]], [[http://www.irregularwebcomic.net/393.html sewage]], [[http://www.irregularwebcomic.net/396.html power]], [[http://www.irregularwebcomic.net/417.html heat output]], [[http://www.irregularwebcomic.net/420.html space]] and [[http://www.irregularwebcomic.net/434.html cooling]]. Unsurprisingly, ''Webcomic/DarthsAndDroids'' also touches on the issue.

* The city planet of Acmetropolis in ''LoonaticsUnleashed''.
* Cybetron in all versions of ''{{Franchise/Transformers}}'' is a machine planet down to its core and is essentially the "body" of Primus, the transformer god with the matrix of leadership being a piece of his soul, making Cybertron a usually dormant GeniusLoci. In some of the animated franchises, Cybertron actually awakes and [[http://upload.wikimedia.org/wikipedia/en/9/9a/Primus.jpg transforms into Primus himself.]]

* Cybertron in ''Franchise/{{Transformers}}'', a machine world from core to surface. The only exception is ''WesternAnimation/BeastMachines'', which shows that Cybertron once supported organic life and ends with the planet transformed into a techno-organic Eden.

!! "BabyPlanet" Examples:

* The city of ''Film/DarkCity'' is a rather unique example - it is a CityPlanet only because it's a world unto itself.

* Creator/IsaacAsimov has a story called ''The Strikebreaker'' about a hundred mile asteroid with a colony - barely started, but already with a fifty thousand people population, fully self sufficient. The story is centered around the supply problem - [[FantasticCasteSystem the man responsible for recycling the waste]] decides to go on a strike.

* The {{Baby Planet}}s from ''VideoGame/RatchetAndClankGoingCommando''.

* Prospit and Derse from ''Webcomic/{{Homestuck}}''.

!! "Plane of Existence" Examples:

* Asgard from ''TheMightyThor'', as well as its [[Film/{{Thor}} movie counterpart]], is a city that encompasses another plane of existence.

* In ''The Concentration City'' by J. G. Ballard, the densely crowded residents can't find an end to the upper and lower floors of the buildings they live in. Train rides out of the city end with you coming back in. Coming back on the same day, the exact same time, as your departure. This is a city that has swallowed everything.

[[folder:Tabletop Games]]
* In ''TabletopGame/DungeonsAndDragons'':
** Dis, the second layer of Hell, is a single, vast city.
** Mechanus, the heaven for LawfulNeutral beings, consists largely of clockwork structures. Some of the gears alone are said to be the size of small continents, and many have buildings built on top of them.
** ''TabletopGame/{{Planescape}}'''s Sigil, City of Doors is a world that happens to be a city, although it's not a planet - it's a dimension.
** The {{Ravenloft}} city of Paridon ''became'' this trope after the Great Upheaval stripped away the countryside that used to surround it, reducing its Island to a pocket of streets and buildings adrift in the Mists. (Not quite a plane, but Ravenloft certainly isn't a planet, so...)
* ''TabletopGame/MagicTheGathering'' has a high fantasy version of this in Ravnica. The city covers the primary planet in one plane of an infinite {{Multiverse}}. %% THIS is how Magic's planes work, people!
** The illustrations on some of the Basic Land cards are particularly impressive, depicting Forests as expansive gardens, Islands as the city's waterways and reservoirs, mountains as the tallest spires and centers of heavy industry, Plains as the suntouched rooftops, and Swamps as the sewers.
** Although the plane didn't used to be that way; in fact, there are still remnants of the wilds on Ravnica, and are primarily the home of the Gruul Clans and some members of Selesnya.
* ''TabletopGame/{{Warhammer 40000}}'' has Comorragh, the city of the Dark Eldar.