In my history, at the year 2070 a billionaire owner of a big corporation is building a private floating city on international water, which has already attracted more than 200 million people wanting to live there, with the promises of individual freedom, almost no street crime, and a safe place to live in this turbulent world suffering after decades of pollution.


  • Everything in this city is powered by electricity: from cars and mass transportation to heating water and houses. Everything is powered by electricity because gas/fossil fuels are not desired.

  • City was built from the beginning to be very energy efficient and always economize when possible. No energy is wasted because the system grid is intelligent enough to distribute/store energy when necessary.

  • And because of that citizens use the average energy a citizen from U.S and UE uses today...What would be the best ways to power this city? I'm thinking about several thorium reactors and solar when possible, but how many reactors would I need? Safer and more efficient reactors than today is desirable.

For food:

  • Plants are grown in massive vertical skyscrapers using aeroponics with 100% optimal conditions and free of diseases 99% of time

  • Animals aren't required anymore; we can just grow their tissues in laboratories free of diseases, much faster, and more nutrient rich.

  • Citizens follow mostly an occidental diet but still I've no idea how many vertical farms I would need to feed 200 million people with abundance.


  • Everything in the city is very efficient and optimized to require the least water possible and consequently less energy too (e.g toilets don't need water anymore).

  • It's a closed system: nothing is wasted, everything is recycled and treated to reuse again on system.

  • The city collects all the rain, and takes water from the ocean, removes the salt, and puts it in the system...because it's a closed system, I just need to add additional water when needed and not keep the constant purification of ocean water.

Industrial goods:

  • They are also building a massive automatized, high technology industry complex to produce most industrial goods (from drugs to car and phones and etc), since buying these from other countries would make country debt too big, and buying raw resources are far cheaper.

Am I missing something? Or can't such a massive city be self-sufficient? I want everything to be the most possible/realistic possible...

I'm building the city using designs and materials tough enough to resist earthquakes/tsunamis/nuclear or bomb attacks. The owning corporation has developed a very resistant and lightweight alloy with the help of nanotechnology that will be used for this purpose.

By self-sufficiency, I mean I want the city to meet most of it necessities alone and only buy from other countries raw materials/resources.

City is funded by the biggest corporation and owner of the project(they have alone 2 trillion dollars of capital) plus almost all countries ( all of them want a little of the tech we are using here) and by a deal with other big corporations (on this history mostly of the biggest companies merged into single powerful corporations) promising them monopoly over some areas.

People floods coming to city because the world is almost a desert now, with many governments becoming oppressive and the third world war is imminent, this city and the tech needed to create is the hope for a better world and future for the humanity itself.


closed as too broad by the_OTHER_DJMethaneMan, bowlturner, Aify, DaaaahWhoosh, ArtOfCode May 11 '15 at 19:09

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ Since they are using ocean water and allow people from the outside into their city, it is clearly not a closed system. $\endgroup$ – Burki May 11 '15 at 13:49
  • $\begingroup$ On a different note: Would you mind re-reading your question and maybe do some tidying? It's a bit difficult to read as it is now. $\endgroup$ – Burki May 11 '15 at 13:49
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    $\begingroup$ "Can such a massive city be self-sufficient?" Well, there's always the basics. Where are you getting building materials from, in sufficient quantities to support a population on the same order of magnitude as that of Brazil (204.3M people per May 11 2015) or 2/3 that of the US (standing at 321M people)? This part (which arguably seems to be the core of your question) may be easier to answer if you are willing to define what exactly you mean by "self-sufficiency". $\endgroup$ – a CVn May 11 '15 at 13:56
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    $\begingroup$ Sorry, but I don't care how advanced your police droids are or how many you own, your gonna have more than a little problem guaranteeing little crime in a city of 200 million people--- 2/3 of the modern U.S. Population. $\endgroup$ – the_OTHER_DJMethaneMan May 11 '15 at 14:19
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    $\begingroup$ @Freedom: Don't know what you mean by "society is desigual", but it seems you have basically no idea about what crime actually is. So start by telling us exactly what 'crime' is in your city: theft, rape, killing from sexual jealousy, having sex with people of inappropriate age/race/sex? How about disrespect for the Dear Leader of your city, or the Prophet of its religion? $\endgroup$ – jamesqf May 11 '15 at 17:15

Am I missing something? Or can't such a massive city be self-sufficiency ? I want everything to be the most possible/realistic possible...

You've missed some really big questions.

1) How is this structurally sound? I'm imagining 2~20Mn boats floating in the ocean, wiped out by a single storm. Let alone a cyclone, tsunami or rogue wave. Google them - they're not easy to ignore.

2) How is this funded. You've made some handwaving statements 'billionaire' 'big company' 'New York'. But I don't think you've thought it through - New York, London and Tokyo have a combined population of ~30Mn... they're not going to fund 200Mn person's worth of floating housing. Assuming a cost of between \$10k and \$100k per person per year, the cost of running this city would be \$2 to \$20 TRILLION dollars! USA's entire GDP is ~\$17T!

3) What is efficiency? I'm not sure why my toilet would be non-flushing - aren't I surrounded by water and power? Can't I easily flush all day long with only a minimal expense? I've rented places with pools - pumped the equivalent of 10,000 flushes a day just for maintenance.

And this all comes down to the biggest question of all:

4) Why? Why would 200Mn people want to come to a big, wet, corrosive, mega-city that's extremely likely to collapse around you, is extremely expensive to live in and has so few natural resources you can't even flush the toilet with seawater?

We need to know these things to be able to suggest appropriate solutions. For example, if this is some sort of hippie commune on mass, then may I suggest all electricity be powered by algae? If it's a technical achievement then something along the lines of nano-tech/fusion/alien inspired may be the answer. Right now we're getting input like:

I'm building the city using materials bought from other countries, that are also used to build nuclear bunkers because a island in international water is very vulnerable and any kind of attack to my critical buildings would put the city on chaos...so i'm building it using designs and materials tough to resist earthquakes/tsunamis/nuclear or bomb attacks.

I'm not sure how your 2070 world works, but I'll tell you how nuclear bunkers are built.

1) Dirt. Lots and lots of dirt. Ideally granite bedrock if possible. If you can, tunnel into a mountain.
2) Concrete. Lots and lots of concrete.
3) Steel. The more the better.

These materials aren't exactly buoyant... and when you consider the shear bulk needed they aren't exactly cheap or ecological either.

  • $\begingroup$ While you are asking the right questions, i think it does not qualify as an answer as defined in the help section. $\endgroup$ – Burki May 11 '15 at 14:19
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    $\begingroup$ @Burki I disagree the OP clearly asked "Am I missing something? Or can't such a massive city be self-sufficiency ? I want everything to be the most possible/realistic possible" and I'm bringing up salient points. Furthermore once we know structure, funding, motivation and a definition of 'efficiency' we can start suggesting energy solutions that suit the world he's building. I'm not sure if we should be using algae generators or antimatter. $\endgroup$ – NPSF3000 May 11 '15 at 14:21
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    $\begingroup$ I think pointing out the holes in the OPs premise is a worthwhile thing... $\endgroup$ – James May 11 '15 at 14:22
  • $\begingroup$ i've edited my question, i didn't added about all this because i tough it would make the question too broad, but i think this community is not so restrict as others...i will add more stuff... $\endgroup$ – Freedo May 11 '15 at 14:30
  • $\begingroup$ give me some time, to finish all aspects that must be addressed $\endgroup$ – Freedo May 11 '15 at 14:34

Am I missing something? Or can't such a massive city be self-sufficient? I want everything to be the most possible/realistic possible...

Yes, you seem to be missing many basic major issues of scale and cause and effect.

  • Not enough technology / design. A self-sufficient futuristic city is called an arcology, and is a very difficult problem even without adding making it float in the ocean, too.

  • Not enough sunlight / food. Sustainable food supply is one of the largest issues, given how many people are in one place, and how little sunlight per person they get, which by the geometry and population density of a city, is hard to get around.

  • Too many people. 200 million people is about half the current population of the United States of America. That's not a city; it's a continent. This multiplies the impossibility of the project by 100 or more. If you don't mind floating on magma rather than water, your floating city already exists: it's called Australia.

  • Not enough time. 2070? When did they start building this continent? The first energy crisis was in the 1970's - you could start in 1980, but that's still only 90 years to build a continent.

  • Not enough resources. There were probably not enough free resources to build a floating continent between 1980 - 2070.

  • Not enough cooperation. You'd need to get most of humanity to agree to give you all their free resources and labor to work on your New Atlantis construction project for those 90 years. If you could get humans to cooperate on building Utopia that way, then you'd no longer have a world conflict crisis to avoid.

  • If you could build your city, you wouldn't need to. Heck, if you even had 200 million good citizens anywhere, you could concentrate on working to solve the planet's problems, create a new economic system, stop pollution, stop GMO pollution, stop war, and just make the whole planet into a utopia. I'd do that instead. Creating a continent-sized engineering project doesn't seem to help anything.

  • Not enough reason. If you really want to be isolated from everyone else, and you have the ability to build a continent, consider just buying Patagonia and southern Chile and constructing a wall to keep the rest of South America out. There are much easier ways to keep other humans away, than building a new floating continent.

  • Earthquakes and tsunamis are both zero-impact in the middle of the ocean. However, ocean storms are very high-impact. Good luck ever doing that.

  • Not flushing toilets is not a major issue here.

  • Nuclear power seems like an unnecessary hazard to me. Use solar, wind & ocean movement.

  • I can't think of any real way to make your floating city nuclear-bomb proof, at all. At best, maybe underwater shelters that can somehow sluff off the pressure of a nuclear torpedo... but multiple torpedoes? I don't think so. You may have survivors, but your sustainable city is not one of them, and the survivors need that to continue to survive. You'd need active countermeasures... but basically I think you'd better focus on not getting attacked with nuclear weapons in the first place.

  • A utopian corporation? A mega-corporation would need to evolve into something very different from a mega-corporation, to be interested in creating a floating continent utopia. The typical corporate / economic error of trying to always "grow" profits, is what is driving destruction of our previously-healthy planet. Escaping corporate-caused home planet death to a corporate paradise makes less sense to me than escaping heroin addiction by taking an overdose.

  • The ultra-rich of the world don't want equality. If they were facing your scenario and feeling nautical, they would probably focus on building themselves resorts with servants... or just use existing cruise ships their corporations already own... somehow making them sustainable... maybe freighters could be converted to farm/solar ships with retractable floating fields and solar panels... um, which would still be impractical, but maybe not as much so, if you're only sustaining ten thousands of elite, and hundred thousands of underlings.

  • Not enough clean water. Converting seawater to fresh water isn't easy to do in large amounts.

  • Too much torque. Skyscrapers are hard to keep standing up on a boat, and even if you could make them stand at all, having them stay up for a hurricane or ocean storm waves seems highly unlikely. Maybe if you could somehow design a flexible framework that would be much wider than it is tall, and could roll with massive waves, that could exist, but I don't know if anything like that has been worked out or is possible. It doesn't sound like 2070 technology to me.

  • No sustainable ecosystem. Earth's ecosystems support life thanks to eons of evolution, in complex symbiotic relationships that involve everything from weather and soil and microbes all the way up to populations of insects, plants, animals, reptiles, mollusks, fungus, etc. Trying to create a new artificial one at sea, is a hard problem you're not likely to succeed at by 2070, even if it were not at sea.

  • Many other things...

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    $\begingroup$ In addition to the not enough sunlight for growing food, the OP is also going into extreme monocultures, which means that the artificially-grown food crops will have all sorts of disease problems. And what does the pollination? $\endgroup$ – jamesqf May 11 '15 at 17:19
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    $\begingroup$ Yes. The full list of issues would go on and on and on. That's a good one to add, though, thanks. $\endgroup$ – Dronz May 11 '15 at 17:21

The term you are looking for is Arcology.

Energy: Since the city is floating, there are 2 really nice powerful energy sources available:

  1. Solar power: Already today we have invented see-through solar panels. You are talking about massive skyscrapers, each of them have windows that act as solar panels. This will generate vast amounts of power without taking up any space.

  2. Wave energy: Having small wires under the city, with small propellers on, will take energy from the currents (this will require for the city to be anchored).


I'm going to assume that you can handwave the structural aspects (meaning, we're going to decide how big this place needs to be to meet goals, and then Science! will figure out how to make it hold together), so let's tackle the obvious: how much space do you need to maintain 200 million people?

First link I found was this infographic regarding how much space you would need to feed yourself. It works out to two acres per person. We're going to handwave a bit and assume that you can save some space with the hydroponics and such, but that you're also going to want parks and offices and the like, and that those two items will balance out - so that our living-and-eating space number is 2 acres per person.

You list 200 million people, so at 2 acres per person, that's 400 million acres, or roughly 1.6 million square kilometers. If this was flat, you'd be looking at something the size of Mongolia or Iran (just to give you a comparison).

Since we're constructing this, we can make a nice geometric shape. A square would be 1200km to the side. If you prefer a circle, it's about 1400km edge to edge. (For reference, the longest supertanker built to date is a touch over 450m long).

Now, you do have some room to wiggle by building up, but I think the takeaway is: you're going to build something at this scale, "floating" might not be the right strategy - you're large enough that it very easily could be simpler to just find some reasonably shallow water and just build your own island. Something this big isn't going to move under it's own power, so might as well park the sucker and be done with it (also, that lets you handwave a lot of the heavy machinery you've got planned)

So, next step - power generation. You are going to need a lot. And since you're building a reasonably small space, I'd say you'd have better luck using the UK number over the US one (it's almost half). But you're going to want every source you can find. Solar is probably the most problematic, since roofing over your city means you'll be spending power lighting everything underneath. But wind, tidal (you're out on the ocean, right?), and nuclear is probably your best bet.

I'm skipping some numbers here because I'm not sure I crunched them right, but it looked like you were going to need a lot of juice. Like, many large reactors worth. So this is another good place to handwave advancement in technology.

Now, just those two issues is going to make this an... interesting project to say the least. But I think where you're going to run into the biggest trouble is your plan to do manufacturing. In addition to the general power, space, and pollution requirements that most manufacturing involves, having to ship everything to and from can't help the bottom line. So, let's take a moment to ask: Why would a megacorp spend such a crazy amount of cash to build what is really a large nation (complete with new landmass) out in the ocean?

The only thing I can think of is a space elevator - those like being out in the middle of nowhere, it's something fancy (and in itself expensive) enough to justify the overall expense, and now you're not a manufacturer, you're an import/exporter (specifically, the only cheap way to and from orbit). If this corp plays it's cards right, the various nations will keep each other away from you (since no-one wants to lose access).


The US, population 300 million has 1060 Gigawatts of power infrastructure. (75% ish) Most of that is coal and gas.

That's not counting power use in transport, that's just wired infrastructure.

But lets assume that your city is vastly more efficient. Each of your 200 million citizens gets by in about 10% of what current US citizens use.
So lets say including transport we need a minimum of 100 Gigawatts of capacity.

Forget solar, it's nice if you have lots of space but cities need many many many times their own area of pannels to run off solar.

You need compact and reasonably clean. So pretty much nuclear. So how much would it cost to set up.


The General Electric ABWR was the first third generation power plant approved. The first two ABWR's were commissioned in Japan in 1996 and 1997. These took just over 3 years to construct and were completed on budget. Their construction costs were around $2000 per KW.

Historically that cost per KW hasn't dropped much because safety requirements have risen. Now you're also going to want your plants to be safe and safety requirements rarely drop so that cost is unlikely to drop much either.

So to just build the power plants for your 200 million people making very generous assumptions about how fantastically efficient it all is it's still going to cost 200 billion dollars just to build the power plants assuming everything goes perfectly.

That's just the power plants. Throw in connecting up all the houses and you've got a big bill.

I'd really suggest knocking a couple of zeros off that 200 million figure if you want to go with the billionaire/rich company backstory.

A planned city of a couple million might be imaginable but you're talking about a megacity larger than London, New York, Tokyo, Paris and most of the other major world cities combined. It's just not practical.


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