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The Walking City was an idea proposed by British architect Ron Herron in 1964. In an article in avant-garde architecture journal Archigram, Ron Herron proposed building massive mobile robotic structures, with their own intelligence, that could freely roam the world, moving to wherever their resources or manufacturing abilities were needed. Various walking cities could interconnect with each other to form larger 'walking metropolises' when needed, and then disperse when their concentrated power was no longer necessary. Individual buildings or structures could also be mobile, moving wherever their owner wanted or needs dictated.
During the building of the U.S. transcontinental railroad, a mobile town of support personnel, restaurants, saloons, and various recreation facilities (laundry, gambling, dance halls, etc.) followed the railroad; the town was colloquially known as Hell on Wheels.
Various types of ships resemble walking cities in function and in scope. Seacraft are the largest vehicles ever built by humans, and the only ones that have reached a scale compatible with Ron Herron's original concept.
Aircraft carriers are the only modern device closely resembling a walking city in concept or scope. An American Nimitz-class aircraft carrier holds just under six thousand crewmen and is over a fifth of a mile long. An aircraft carrier could be considered a walking city whose primary resource or function is that of an aircraft maintenance, supply and launching center which moves about the globe fulfilling its function where it is most needed while stopping occasionally for resupply (Glassco, 2004).
The world's largest cruise liners are also equipped to hold thousands of people, with all the amenities of modern life - including shopping malls, ice rinks, radio and television stations and wedding chapels; however, they are not intended for the extended living that military vessels such as aircraft carriers are.
After audacious projects such as the Freedom Ship have failed, the only serious attempt to emulate a floating city is Seasteading, which aims to create permanent dwellings at sea, outside the territories claimed by the governments of any standing nation.
Geoffrey A. Landis proposed in 1989 that a mobile base or city on the moon could move to remain constantly in sunlight, allowing the use of solar power and avoiding the darkness and cold temperatures of the lunar night. He later suggested that the same concept could be used on the planet Mercury, where a mobile base or city could be used to avoid sunlight by staying in the temperate twilight region near the terminator, although this concept had previously been anticipated by the science fiction writer Kim Stanley Robinson in 1986.
- The four novels in Philip Reeve's Mortal Engines Quartet (Hungry City Chronicles) include large mobile Traction Cities that travel across the world, devouring each other to gain fuel and other resources.
- A massive city travelling along equatorial rails around the planet Mercury is the setting for a minor part of Blue Mars, the last book in the Mars Trilogy of Kim Stanley Robinson. The city is pushed along by the slight yet powerful expansion of the rails as the close-by sun shines on them (with the city always just staying within the planetary night), moving the city once around the planet every 88 Earth days. The same city appears in Robinson's early novel The Memory of Whiteness.
- There is a similar arrangement in Timothy Zahn's Heir to the Empire, where Nomad City avoids Athega's light by continually moving over the surface of Nkllon.
- In Alastair Reynolds's Absolution Gap, vast cities circle the moon of Hela to keep the planet Haldora in view, in case "the Miracle" – the momentary disappearance of Haldora – occurs again. The mobile cities are called Cathedrals and are devoted to worship of the Miracle, which they believe is God's message to humanity.
- In Christopher Priest's novel Inverted World a city on a "hyberbolic" planet is continually moved on rails to keep it at a particular location—which itself moves—where conditions are "normal".
- Greg Bear's novel The Strength of Stones is set in the declining years of a planet of motorized cities that ejected their inhabitants.
- Storm Constantine's novel Calenture takes place in a world of mobile cities that fly, walk or move on wheels, guided and powered by "pilot stones".
- The computer game Starcraft features an interstellar empire of humans that use collections of mobile buildings (able to fly slowly with vertical takeoff and landing) to assemble ad-hoc cities in space and on land.
- In Dark Heresy, a roleplaying game set in the Warhammer 40,000 universe the city of Ambulon on the planet Scintilla is build on the back of a giant walking machine, found there by the imperial settlers. It roams the planet's wastelands, mining and harvesting natural resources which then are delivered to other cities.
- In the anime series Chrome Shelled Regios, Regios are large domed mobile cities created by humans to live in after the Earth's atmosphere became too polluted to live in. They move to gather resources, meet other cities, and flee from giant monsters.
- In Jules Verne's Propeller Island, Milliard City is built on a massive ship in the Pacific Ocean and is inhabited entirely by millionaires.
- G.A. Landis, "Solar Power for the Lunar Night," NASA TM-102127, Geoffrey A. Landis; 9th Biennial SSI/Princeton Conference on Space Manufacturing, (abstract) 1989
- G. Landis, "Proposal for a Sun-Following Moonbase," Journal of the British Interplanetary Society, Vol. 44, pp. 125-126 (1991).
- Kim Stanley Robinson, The Memory of Whiteness, ISBN 0-8125-5235-0, Tor Books (1986)
- Robert Zubrin, The Case for Mars, ISBN 0-684-82757-3 (1996)
- Landis, Geoffrey. "Proposal for a Sun-Following Moonbase," Journal of the British Interplanetary Society, Vol. 44, pp. 125–126 (1991).
- Glassco, John. "And The City Just Walked Away", Venue Magazine, 2004