This article was compiled by Ross Smith of New Zealand. The original article can be found here.

SPOILER WARNING: For obvious reasons, this list must necessarily contain spoilers for many of the books described. You have been warned.


I've always been fascinated by the science fiction idea of the "megastructure", a gigantic artificial structure that can serve as the background for all kinds of interesting stories. ("Megastructure" is my own word for the idea; David Gerrold calls it "the Enormous Big Thing".) I've assembled this list of all the megastructure stories I could remember, with a brief description of each. If you have any additions, corrections, or comments, please add them to this list (in particular, I'd like to get dates for all of the novels mentioned).

The best-known megastructure novel, of course, is Larry Niven's Ringworld (1970). Niven also wrote an article, "Bigger than Worlds", which can be found in his collection A Hole in Space (1974); he describes many different kinds of structure, and goes into interesting details such as how to build a Ringworld. (You dismantle the planets, one at a time, and use the material to make disc-shaped plates, orbiting the sun and linked by cables, then move the inhabitants of the next planet to the plates while their planet is being dismantled; eventually you join all the plates into a ring. See also The Player of Games by Iain M Banks.)

But the very first author to make use of megastructures (to the best of my knowledge) was Olaf Stapledon, whose classic novel Star Maker (1937) describes many of the ideas (in this and other areas) that would later be rediscovered by other writers and hailed as original (including the star-girdling sphere that is usually attributed to Freeman Dyson).

My current best attempt at a definition of a megastructure is: "An artificial structure (this is intended to include living creatures) which: (1) Has either a length of at least 1000 kilometres or a surface area of at least 10,000 square kilometres; (2) Requires materials or construction techniques beyond the capability of 20th century technology; (3) Is either a single object, supported by its own strength, or a stable cluster of objects in space."

Note that clause 2 is intended to exclude such things as solar sails (which can be large but are theoretically within our reach now, so they don't "feel" like SF megastructures to me), and clause 3 is intended to exclude planet-covering cities such as Isaac Asimov's Trantor, which don't really count as single structures.

The list of books is divided into two sections: first, books which are primarily about megastructures, and dominated by one or more particular structures; and second, books in which megastructures are mentioned, but are not central to the story.

Thanks to everyone who helped me compile this list, especially Eric Max Francis and Sinya B Schaeffer.

Classification of Megastructures

This is based to some extent on the classification in Niven's article. The types are arranged in approximate order of increasing size.

  • Hollow World: An asteroid (or something similar) hollowed out and set

rotating for artificial gravity, with landscaping on the inside. It may or may not be fitted with some form of propulsion system as well. The idea is an old one in SF, and it's probably impossible to find out who first thought it up.

  • Orbital Tower: In its simplest form, a very strong cable lowered from a

synchronous satellite to the surface of the Earth (or another planet, of course). Usually a second cable extends outwards, with an asteroid or something similar on the end as a counterweight. There are many variations on this theme. The first SF novel to use it was almost certainly [[Arthur C. Clarke]]'s The Fountains of Paradise (1979), but the idea goes back decades in astronautical literature.

otherwise similar in size and shape to a natural planet such as Earth. It may or may not be recognisable as artificial from the outside. An old SF idea, probably first used by Olaf Stapledon in Star Maker (1937).

  • Discworld: A flat disc, comparable in surface area to an Earthlike planet.

One side or both may be populated. The idea was thought up by [[Terry Pratchett]], probably inspired by the Alderson disc (see below), and as far as I know his novel Strata (1981) is the only appearance of the idea in written SF (although one appears in the graphic novel Starstruck (1984) by Elaine Lee and Michael William Kaluta, and of course Terry has since written a very successful series of fantasy novels based on a related concept).

  • Rosette: Several planets or planet-sized objects orbiting each other in a

circle; there may or may not be another object at the centre. The first SF use of the concept is probably in Larry Niven's Ringworld (1970) (incidentally, Niven's claim that such a system would be stable is false). The "order" of a rosette is the number of objects (e.g. the Puppeteer rosette in Ringworld is order 5).

normal planet and a Dyson sphere (see below). The first appearance of such an object in SF (and the only one, to my knowledge) is Tony Rothman's [[The World is Round]] (date?).

  • Topopolis: A long, cylindrical object, rotating for gravity, and wrapped

around a star in a spaghetti-like mass (or mess). The concept was invented by Pat Gunkel and mentioned by Larry Niven in "Bigger than Worlds", but as far as I know nobody has yet had the audacity to write a story about it (unless you count Greg Bear's Eon and Eternity, which describe a vaguely related concept).

  • Ringworld: A circular ribbon, very strong, rotating for gravity, with a

star at the centre. The idea was thought up by Larry Niven and first used in his novel Ringworld (1970). It was later pointed out to him that the Ringworld would be unstable and would require some form of active control system to keep it centred on its sun. This resulted in two more books written for the series describing such a system.

  • Alderson Disc: A massive disc the size of a planetary system, with a small

hole in the centre through which a star bobs up and down. Different intelligent species, with different temperature requirements, would live at various distances from the centre. Thought up by Dan Alderson and mentioned by Larry Niven in Bigger than Worlds; as far as I know it has never been used in a story (the idea is mentioned, as a hypothetical possibility that has never been built, in Terry Pratchett's Strata (1981)).

  • Dyson Sphere: An artificial sphere the size of a planetary orbit. There

are two distinct forms. The original version (which I call "type I") consisted of a vast number of small structures, travelling in separate orbits and surrounding the Sun so densely that no light escapes; this is generally attributed to scientist Freeman Dyson, although Dyson himself admits to having borrowed the idea from Olaf Stapledon's novel Star Maker (1937). The second version ("type II"), more common in SF, is a solid, continuous sphere; people may live on either the inside or the outside (or, occasionally, both). The earliest appearance of this version that I know of was in Robert Silverberg's novel Across a Billion Years (date?). One appears in an episode of Star Trek - The Next Generation (Relics), but it hasn't reached these shores yet.

Novels About Megastructures

(I've made a token attempt to give specific spoiler warnings by marking entries that contain major spoilers for the novel in question with "**". In some cases, of course, the mere presence of a title in this list is a major spoiler in itself; there's not much I can do about that.)

Author:  Greg Bear
Title:  Eon (1985)
        Eternity (1988)
Type:  Variation involving features of the hollow world and topopolis
Description:  From the outside it appears to be an asteroid, but on the
inside it's an (apparently) infinitely long cylinder, with occasional
openings leading to various points in space and time.  A city occupies part
of the axis.
   Author:  Greg Bear
   Title:  _Hegira_ (1979) **
   Type:  Dyson sphere (type II)
   Description:  A sphere constructed in the distant future and displaced

into a pocket universe of its own, to ensure the survival of humanity through the destruction and rebirth of the "real" universe.

   Author:  Terry Bisson
   Title:  _Wyrldmaker_ (1981) **
   Type:  Rosette (order 3)
   Description:  A spaceship on a centuries-long voyage to "seed" other

planets with life; it consists of three artificial worlds, with a control station at the centre.

   Author:  Jack Chalker
   Title:  _Midnight at the Well of Souls_ (1977)
           _Exiles at the Well of Souls_ (1978)
           _Quest for the Well of Souls_ (1978)
           _The Return of Nathan Brazil_ (1980)
           _Twilight at the Well of Souls_ (1980)
           (two more books whose titles escape me)
   Type:  Artificial planet
   Description:  A planet that is actually a giant computer, used by the

ancient Markovians to create most of the other life forms in the Galaxy (including humans). The surface is divided into 1260 hexagonal regions, each inhabited by a different intelligent species.

   Author:  Arthur C Clarke
   Title:  _The Fountains of Paradise_ (1979)
   Type:  Orbital tower
   Description:  The book describes the construction of the first orbital

tower, made of an artificial fibre based on diamond. In later centuries, the original tower and five others are combined with an orbiting ring to form a structure resembling a gigantic ship's wheel. (A full description, with dimensions, is given in the book; unfortunately my copy is currently AWOL.)

   Author:  Arthur C Clarke (and Gentry Lee in second and following books)
   Title:  _Rendezvous with Rama_ (1973)
           _Rama II_ (1989)
           _The Garden of Rama_ (1991)
           _Rama Revealed_ (1993)
   Type:  Hollow world
   Description:  A huge alien starship enters the Solar System, and is

investigated by the crew of the only ship able to intercept it, with the occasional help of some back-seat scientists on Earth. They find all sorts of strange things inside, but no sign of the aliens who built it. In later books more ships are encountered (but I haven't read them and probably never will).

   Author:  Philip Jose Farmer
   Title:  _Inside Outside_ (date?) **
   Type:  Hollow world
   Description:  A hollow world created by the alien "Ethicals" is used to

test human souls before birth. (The book is a "prequel" to the Riverworld series.)

   Author:  Harry Harrison
   Title:  _Captive Universe_ (date?) **
   Type:  Hollow world
   Description:  A hollowed asteroid is sent on an interstellar voyage,

inhabited by a primitive society descended from the Incas; in order to keep the nature of their world secret, their intelligence is kept artificially low by genetic engineering.

   Author:  Colin Kapp
   Title:  _Cageworld 1:  Search for the Sun_ (date?)
           _Cageworld 2:  The Lost Worlds of Cronus_ (date?)
           _Cageworld 3:  The Tyrant of Hades_ (date?)
           _Cageworld 4:  Star-Search_ (date?)
   Type:  Dyson sphere (type II)
   Description:  In the distant future, the Solar System has been

transformed into a series of concentric shells (one for each planet, plus an extra one between Saturn and Uranus, if I remember rightly). People live on the outer surface of each sphere, and have forgotten about the outside universe. Dimensions of the system (overall): diameter 12 billion kilometres; mass 5.2e36 kilograms (2.6 million Suns).

   Author:  John C McLoughlin
   Title:  _Toolmaker Koan_ (1988) **
   Type:  Hollow world
   Description:  A hollow asteroid, built by a long-extinct people and

controlled by an artificial intelligence from another dead world, is found by humans, themselves the last survivors of nuclear war on Earth. The three peoples attempt to cooperate to ensure their survival, against all the evidence that says that intelligent species inevitably destroy themselves. Dimensions: length 380 kilometres; diameter 30 kilometres; mass is given as 2.7 billion tonnes but this is much too small for its size (by perhaps a factor of 1000).

   Author:  Larry Niven
   Title:  _Ringworld_ (1970)
           _The Ringworld Engineers_ (1980)
           (third book in preparation)
   Type:  Ringworld; also mention of a rosette (order 5)
   Description:  The canonical ringworld, as described above.  A set of

"shadow squares" surround the sun, providing a day/night cycle on the surface. Dimensions: diameter 306 million kilometres; width 1.6 million kilometres; mass 2e27 kilograms (330 Earths); rotation period 9.375 Earth days; surface gravity 0.94 Earth gravity (the figure given by Niven in the second book is incorrect). The ring is made of a very dense material called "scrith", whose strength must be comparable to the forces that hold the atomic nucleus together (!).

   Author:  Frederik Pohl & Jack Williamson
   Title:  _Farthest Star_ (1975) **
           _Wall Around a Star_ (1983) **
   Type:  Dyson sphere (type II)
   Description:  Object Lambda, alias Cuckoo, is approaching our Galaxy at

a sixth of lightspeed. A scientific team is sent on a one-way trip via matter transmitter/duplicator, and discover it to be a gigantic "lifeboat" from an exploding galaxy. Dimensions: diameter 600 million kilometres; mass 1.3e32 kilograms (66 Suns); surface gravity 0.01 Earth gravity (the effect of low gravity on human evolution is an important part of the story).

   Author:  Terry Pratchett
   Title:  _Strata_ (1981) **
   Type:  Discworld; also mention of an orbital tower
   Description:  A flat disc whose surface is formed into a map of the

Earth, enclosed in a sphere with stars painted on the inside. Made by the creators of the universe, as an intentional flaw in their creation. Dimensions: diameter 21,000 kilometres; mass 8.1e24 kilograms (1.4 Earths); surface gravity 1.0 Earth gravity.

   Author:  Tony Rothman
   Title:  _The World is Round_ (date?)
   Type:  Superplanetary sphere
   Description:  Patra-Bannk is an artificial world, much larger than a

planet, but orbiting a star in the normal way. A black hole forms its core, power source, and high-tech materials factory.

   Author:  Bob Shaw
   Title:  _Orbitsville_ (1975)
           _Orbitsville Departure_ (1983)
           _Orbitsville Judgement_ (1990)
   Type:  Dyson sphere (type II)
   Description:  A solid sphere surrounding a star, built by an ancient

alien species, apparently as a kind of trap for intelligent beings, for unknown reasons (I haven't read all the books, so I don't know all the secrets). A cage-like structure around the sun provides a day/night cycle for the landscape that covers the inner surface.

   Author:  Charles Sheffield
   Title:  _The Web Between the Worlds_ (1979)
   Type:  Orbital tower
   Description:  Generally similar to the one described by Arthur C Clarke

in _The Fountains of Paradise_. Sheffield's "beanstalk" is assembled in space and anchored to the Earth's surface in a complicated and dangerous orbital manoeuvre; I'm inclined to agree with Clarke that Sheffield's method would never be allowed.

   Author:  Brian Stableford
   Title:  _Journey to the Centre_ (date?)
           _Invaders from the Centre_ (1990)
           _The Centre Cannot Hold_ (1990)
   Type:  Artificial planet
   Description:  Asgard appears to be an Earth-sized world with a frozen

surface, but is actually a huge artifact, with thousands of internal levels, some abandoned, some inhabited by various kinds of alien.

   Author:  John Varley
   Title:  _Titan_ (date?)
           _Wizard_ (date?)
           _Demon_ (date?)
   Type:  Hollow world
   Description:  A wheel-shaped object, found orbiting Saturn, turns out

to be a living thing, an intelligent world with various peculiar creatures living inside.

                              Other Novels
   Author:  Douglas Adams
   Title:  _The Hitch-Hiker's Guide to the Galaxy_ (date?) **
           _The Restaurant at the End of the Universe_ (date?)
           _Life, the Universe, and Everything_ (date?)
           _So Long and Thanks for All the Fish_ (date?)
           _Mostly Harmless_ (1992)
   Type:  Artificial Planet
   Description:  The Earth is actually a gigantic computer, commissioned

by mice (who are actually hyper-intelligent pan-dimensional beings) and built by the planetary engineers of Magrathea, in order to figure out the Question to the Ultimate Answer.

   Author:  Brian Aldiss
   Title:  _Hothouse_ (1962)
   Type:  Orbital tower (variation)
   Description:  Billions of years from now, the Earth and Moon are linked

by immense webs built by huge, spider-like creatures descended from plants.

   Author:  Iain M Banks
   Title:  _Consider Phlebas_ (1987)
           _The Player of Games_ (1988)
   Type:  Ringworld
   Description:  Several "Orbitals" (small ringworlds) appear in these

novels, including one under construction, using the method described by Niven in "Bigger than Worlds". The first book describes the spectacular destruction of a ringworld by "controlled hypergrid intrusion".

   Author:  Steven Barnes and Larry Niven
   Title:  _The Barsoom Project_ (1989)
   Type:  Orbital tower
   Description:  A proposal for building an orbital tower on Mars, to help

with a terraforming project.

   Author:  Gregory Benford
   Title:  _Beyond the Fall of Night_ (date?)
   Type:  Orbital tower (variation)
   Description:  A living creature, tens of thousands of kilometres long,

spins end over end, the ends alternately touching the Earth's surface and then flinging whatever was picked up into space. It was created as a kind of self-repairing orbital elevator.

   Author:  Gregory Benford
   Title:  _Tides of Light_ (date?)
   Type:  Orbital tower (variation)
   Description:  Essentially identical to the creature in _Beyond the Fall

of Night_ (I think this book actually came first).

   Author:  Lloyd Biggle Jr
   Title:  _Watchers of the Dark_ (1966) **
           plus several sequels
   Type:  Artificial planet Description:  The planet Primores, seat of the

galactic government, turns out to be a giant computer, Supreme.

   Author:  David Brin
   Title:  _Sundiver_ (date?)
   Type:  Orbital tower
   Description:  Two "needles" which carry passengers and freight between

earth and orbit are briefly mentioned.

   Author:  Harry Harrison
   Title:  _Star Smashers of the Galaxy Rangers_ (1973)
   Type:  Ringworld
   Description:  A ringworld, apparently similar to Niven's, was built to

provide living space for an expanding civilisation. When the two edges of its growth meet on the far side of the ring, thousands of years later, a vicious war breaks out.

   Author:  John C McLoughlin
   Title:  _The Helix and the Sword_ (1983)
   Type:  Hollow world
   Description:  In the year 7758, humanity is spread across the Solar

System in 74,922 "Islands", engineered life forms resembling huge versions of O'Neill-style space colonies; the Earth has been abandoned, and inorganic technology is a near-forgotten legend.

   Author:  Kim Stanley Robinson
   Title:  _Red Mars_ (date?)
   Type:  Orbital tower
   Description:  Phobos is used as a counterweight for one end of an

orbital tower. [Haven't read this; thanks to David Goldfarb for details.]

   Author:  Robert Silverberg
   Title:  _Across a Billion Years_ (date?) **
   Type:  Dyson sphere (type II)
   Description:  A team of archaeologists, searching for the remains of a

vanished civilisation, finds it in a giant artificial world.

   Author:  Olaf Stapledon
   Title:  _Star Maker_ (1937)
   Type:  Dyson sphere (type I); also mention of artificial planets
   Description:  An epic history of life in the universe, describing many

kinds of artificial world, including what later came to be referred to as Dyson spheres.


-- ... Ross Smith (Wanganui, New Zealand)