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Ring World Planet

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"This world. Looping. Repeating... forever. Is it a symbol of life or a cruel joke by the Forerunners?
Escharum, Halo Infinite

One of the World Shapes more often found in Science Fiction than in Fantasy, a Ring World Planet is a world in the shape of a concave cylinder. The horizon curves up, not down, but only in one dimension, meaning that the ground in that direction would be "uphill"note  unless the ring is large enough that the curve is impossible to notice over small distances. The sides of the cylinder will be walls, with or without a "ceiling." These can range in size from the equivalent of a true Dyson Sphere to a cylindrical space station in planetary orbit. These variants of worlds usually at least pay some lip service to the known laws of physics, since a spinning ring generates a centrifugal force that could be used instead of gravity. However to exist for real, particularly large ones over a few dozen kilometers would have to be made of Unobtainium.


Note that it would always be "day" in such a cylindrical world unless measures are taken to simulate day and night, either through sun shades, mirrors, or some combination of the above. Another alternative is choosing an orbit where the ring periodically gets shadowed by something. Orbits that use the Earth for this would produce night about every 90 minutes (ISS altitude) or a few minutes every few months (a typical geostationary orbit, about the same frequency as a lunar eclipse).

These were formerly referred to as "Niven's Rings" by physicists, astronomers, and science fiction writers, after the Trope Maker, author Larry Niven (who thought it up as a mid-point between a Dyson Sphere and a planet), in his novel Ringworld, but, following feasibility studies, have since adopted proper nomenclatural names of "Stanford Torus", and, for the larger version, "Bishop Ring," while the term "Niven's Ring" remains the designation for colossal megastructures with a star in their center.


Compare Planet Spaceship, and the super-trope Centrifugal Gravity.


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    Anime and Manga 
  • Gundam:
    • The franchise helped popularize the O'Neill Cylinder space colony (see below in "Literature"), as well as other designs.
    • Actual ring shaped colonies (known as the "Stanford Torus" or "Island 2" model) are only common in the Gundam Wing continuity, though one also shows up in Gundam Unicorn, which was apparently the first ever built in the UC-verse and promptly got blown up.
  • In Voices of a Distant Star, the Lysithea briefly docks at a ring-shaped space station built around a moon, which Words of Love/Across the Stars states is Europa.
  • In Cowboy Bebop, most space stations are ring-shaped.

    Comic Books 

    Fan Works 
  • A Crown of Stars: Several artificial worlds of the Empire of Avalon are built like this. Shinji and Asuka see several of them as soon as they step through the dimensional portal.
  • In Urohringr, part five of Austraeoh, it turns out that the world Equestria is in is one part of a great, shattered ringworld named Urohringr.

  • Possibly the most famous example, the space station from 2001: A Space Odyssey, although this is on a much smaller scale with a different purpose.
  • The titular space station of Elysium appears to be a Stanford Torus.
  • Most of the changes made to the novel for the film Starship Troopers were execrable, but one of the ones that wasn't was a spaceship docking ring surrounding the entire Earth linked to the surface by space elevators.
  • Interstellar: By the end of the movie, humanity managed to leave Earth and starts inhabiting giant space stations that resemble a Stanford Torus.
  • Moonfall: In the projection shown to Brian, we saw a ringworld habitat.

  • Larry Niven's Ringworld is set on a world shaped like a vast ring with a sun at its center. It's made of Unobtanium called scrith and is so massive that its geographical features include 1:1-scale maps of several planets (including Earth). These maps are significantly less than 1% of the ring's surface area. Day and night is created by massive solar panels in spinning in orbit between the sun and the ringworld. Bussard ramjets on the rim of the ringworld keep it centered. The whole thing is reasonably Ragnarok Proof, which is good, as it's also quite Ragnarok-prone: once high-technology civilization there collapses, the absence of available metals means that it can never arise again without outside interference.
  • The Culture of Iain M. Banks's novels builds Ringworld-style Orbitals (but smaller) as housing for many of its citizens. They have a few full size, fits-round-a-star Ringworlds too but they're much rarer, since you can get more useable area by using the same mass to build orbitals so most of the Culture regards them as tacky.
  • Arthur C. Clarke's Rama from the series started by Rendezvous with Rama, is a massive cylindrical spacecraft.
  • The protagonists of Gregory Benford's Beyond Infinitynote  spend a brief time trapped in a Tunnelworld after an encounter with some 4-dimensional aliens. It was a closed loop, so traveling in any direction for a long enough time would return you to your point of origin.
  • Gerard O'Neill proposed a real world cylindrical space colony: Island Three.
    • The page image is a representation of the "Stanford Torus", another design inspired by both O'Neill's work and the classic "wheel-and-hub" space stations.
  • Earth in Illium and Olympos is surrounded by two huge ever moving rings. They are not fun places.
  • In Voidskipper most people live in these, albeit usually the planet-sized kind rather than the solar system sized variety. They get around the lack of materials stronger than carbon nanotubes by having the rotating part supported by a static shell, connected by a magnetic bearing.
  • Thistledown, from Greg Bear's The Way Series, is a hollowed out asteroid containing seven cylindrical chambers separated by bulkheads. The seventh chamber connects to a cylindrical pocket universe with several million miles of terraformed interior.
  • The Titans in John Varley's Gaea Trilogy are living ringworlds.
  • In For Your Safety the Groupmind builds a Ring around Earth for the humans it had to overthrow in order to save, where they can live in peace under its watchful eye. Though construction time is estimated at 1500 years so the humans have to be put in stasis until then.
  • The Neyel in Star Trek: Titan are a human Lost Colony named after the O'Neill habitats they originally settled in.

    Live-Action TV 
  • In the fifth episode of The Book of Boba Fett, Din Djarin travels to an ecumenopolis version of these called Glavis to both collect on his bounty and reunite with his sect of Mandalorians. The day/night cycle appears to be very quick, with bands of sunlight and night moving quickly over the ring's surface.

  • Iolara from Jemjammer is the hatchery for many spacefaring Lizardfolk and used to be a ringworld. However at some point it was broken into multiple pieces, though they are still in orbit around the star.

    Tabletop Games 
  • Dungeons & Dragons:
    • Sigil from the Planescape setting is a small version of this with the inner surface completely covered by city, and floating on top of an infinitely tall spire in one of the Outer Planes. It's also a sort of hub that connects to all the other planes of existence.
    • There's also Penumbra, the illithid homeworld, which is an Alderson disk note . It may or may not exist yet.
  • In Eclipse Phase many people following the Fall live in space habitats, many of the bigger ones are toruses or O'Neill cylinders. However there's also a number of habitats that don't bother with spinning since basic biomods counter the degeneration from microgravity.
  • Cyberpunk 2020: As of 2025 there are five ESA built orbital colonies located at the Lagrange points of Earth-Moon system:
    • The Crystal Palace at L1 is a cross between the classic rotating wheel space station and a Stanford torus. It consists of five rings, a central hub and two giant mirrors illuminating the transparent roofs of the two outermost rings.
    • Two O'Neill cylinders, O'Neill One and smaller O'Neill Two (Galileo Cylinder), are located at L5 and L3 respectively. Originally built and controlled by ESA, those two habitats later rebelled and declared independence.
    • The newest cylinder, O'Neill Three (Paradise Station) at L4note , is still run by ESA which maintains a martial law since the rebellions.
    • Finally, at L2 there's a much smaller testbed cylinder which currently serves as deep space craft construction facility.

    Video Games 
  • Halo: The seven titular ringworlds, which resemble Banks's Orbitals, are superweapons designed to kill off all sapient life in the galaxy. The entirety of Halo: Combat Evolved takes place on one of these Halos (Installation 04), which is located at the Lagrange Point 1 note of a gas giant and its moon. All six other Halo ringwords appear to have originally orbited gas giants as well, though Installation 03 eventually found itself somehow orbiting a rocky planet instead.
  • In Star Fox Zero, Area 3 is a "Stanford Torus" space colony.
  • Startopia has you turn several of these into profitable space stations. Apparently, all known races use the same exact design for their space stations, right down to the color scheme. They were originally built by a galactic empire that has since fallen, and a big part of your job is getting them into a usable state.
  • EV Nova has several of these, mostly ring-around-a-planet style. Though one is (for all intents and purposes) THE Ringworld. (The Polaris use that one for effectively infinite farmland.)
    • For bonus Shout-Out points, that ringworld is named Tre'ar Helonis.
  • Mass Effect:
    • The Citadel is one of these. In particular, the Presidium is a huge ring with its own biosphere and simulated sky at one end of the space station.
    • The Alliance's Arcturus Station is described as a Stanford Torus.
  • You can make these in the Space Empires series. A Dyson Sphere is better, though.
  • Some of the planets in both Super Mario Galaxy and Super Mario Galaxy 2, such as the planet in which you fight Megahammer (a Humongous Mecha piloted by Bowser Jr.) on in the latter, actually look like these.
  • You can build these in Star Ruler, admittedly as a lategame option. They are Capital-H Huge, larger than some planetary orbits.
  • Shores of Hazeron has ancient ringworlds which can be colonized. The ringworlds are almost exactly like those from the Ringworld novel, with mountains flanking the inner walls, and with shadow squares creating day/night cycles on the surface. Ringworlds have the advantage of being able to carry far more population than a planet, and having 7 different resource zones - if the ore is bad in one zone, it may be high quality in the next one over. Additionally, since the ringworlds are all centered around the sun, and wormholes are always near the sun, any defenses installations on the ringworld will immediately be able to concentrate their fire on anything entering the system via wormholes.
  • X:
    • The Torus Aeternal in X3: Terran Confict is a massive space station ringing Earth's equator. It serves as a docking ring, shipyard, and orbital defense station. In X3: Albion Prelude, it gets blown up.
    • The Teladi Union's space station in X Rebirth has a centrifugal habitation ring that is over a dozen kilometers wide. The ring has an artificial atmosphere contained by energy shields, and alternates between manufacturing sectors and park-like habitation sectors.
  • In Stellaris, Fallen Empires sometimes have ringworlds build around stars, and one will occasionally find heavily-guarded ring worlds serving as nature preserves (complete with primitive civilizations).
    • In the "Utopia" DLC it's possible to build ringworlds late in the game in planet-rich (though not necessarily inhabitable) star systems, dismantling the planets in the process. Dyson Spheres are also buildable for a massive energy boost.
  • Kiengir, the primary setting of Axiom Verge 2, is one of these. This is most easily noticeable in Irikar, where you can see the cratered surface of the ring's opposite end.

    Web Original 
  • The world of Pendor, from The Journal Entries of Kennet Shardik, is Niven's Ringworld with the Serial Numbers Filed Off, because Niven had threatened to sue Elf Sternberg over writing gay BDSM Known Space fanfic.
  • Darwin's Soldiers: Card of Ten takes place primarily on one of these.
  • So many space habitats in Orion's Arm. There are even Banks Orbitals, named in honor of Iain Banks in-universe. Star-encompassing rings may be found in some systems, but only around small stars like white dwarfs. There are also variations such as diskworlds (complete disks rather than rings, a shape which gives a lot more living space for the same diameter) and topopolises (essentially O'Neill cylinders extended all the way around a star so the two ends meet, resulting in something similar to Niven-style ringworlds but without needing extremely strong materials).

Alternative Title(s): Ring Shaped World