The in-universe solution to the Infinite Sea problem, crossing millions of kilometers of landless ocean, is actually "create a flying island of X acres and take the trip in style" because there is simply that much magic in the setting and it's that easy to do the "flying island" shtick. Also because wizards are the only people in that world with a real curiosity about what is over the horizon, and why would they risk sea sickness.

Given that it's easy to get such a flying island state into the air but impossible to provision it with food and craftsmen etc. using magic I wonder how big X needs to be to create a self-sustaining high medieval city-state that can supply all its own food and fuel, in the form of wood and its products. A limited supply of things like potters clay, building stone for repairs, and metals and/or their ores, can be brought in but for the rest the state is effectively cut off.

Assuming a late medieval agricultural environment, including arable crops, livestock, woodlots and hedgerows, and complete with occasional total crop failures, etc., in a mild, well-watered climate, on fertile soil how much land would an island state need to sustain the full social spectrum of a feudal hierarchy (so a near absolute ruler, a landed gentry, and the merchant/artisan and peasant majority).

Given this excellent answer I don't in fact need a land area so much as a population. My understanding is that single fiefs were never self-sufficient for much more than the bare necessities. Although they often supplied the raw materials for some luxuries to their feudal overlords which were processed in specialist workshops like wineries located close to the seat of the local Baron. Even single baronies seem to have needed to trade for many luxuries, some produced good wines, others fine cheeses etc., and they traded for the goods they did not themselves produce. So the question becomes one of how many people it takes to make a self-sufficient kingdom, albeit a small one?

The state will be effectively coastal for the purposes of a fishing fleet but the numbers given in Mołot's answer don't change much if at all because of this so it's still a matter of the population to sustain the crafts and land use diversity to supply the kingdom (wizarddom?) with everything it needs in the form of both the essentials and the luxuries of life.

Please note specifically that while the island itself is a magical construct the means of supporting the population on it cannot be.

In case it makes a difference the state will not need a standing army for the trip although the equipment for a militia levying all able-bodied adults will be maintained.

Special thanks to the people who helped me sandbox this, the original didn't really ask the right question.

  • $\begingroup$ This seems a lot like the classic small-colony-in-a-bottle question. Are you saying that the flying-state must trade for small-settlement basics like food, water, wood, leather, clay, fuel, etc? Is what they provide to others in trade worthwhile? While flying over the endless sea, is there a reliable source of freshwater? While over somebody else's territory, is there reliable (non-obnoxious) disposal for sewage and trash? $\endgroup$
    – user535733
    Jul 1, 2018 at 16:43
  • $\begingroup$ @user535733 I'm asking how big it has to be so it doesn't have to trade for anything that isn't mined, since mining a floating rock gets to be a bad idea very quickly. The question clearly states that the land is well watered so yes freshwater is a given. $\endgroup$
    – Ash
    Jul 1, 2018 at 16:47
  • 1
    $\begingroup$ @user535733 Waste disposal over someone else's territory isn't a problem, The flying island is flying over an infinite sea. $\endgroup$
    – a4android
    Jul 2, 2018 at 5:05
  • $\begingroup$ Is fishing a possibility? The numbers change dramatically if fishing / extracting resources from the sea is a possibility. I'm kinda liking the imagine of many small elevators handing off the bottom of the island $\endgroup$
    – Chromane
    Jul 2, 2018 at 5:29
  • $\begingroup$ @Chromane "The state will be effectively coastal for the purposes of a fishing fleet but the numbers given in Mołot's answer don't change much" so yes fishing is possible but it doesn't actually change the answer to the question which is how many people does it take to run a small but complete feudal state. $\endgroup$
    – Ash
    Jul 2, 2018 at 10:25

2 Answers 2


The major advantage your "flying island" has it that it can be essentially custom built from the ground up for one purpose - to sustain the population/crew and wizarding rulers/captains on their long journey. It's a command economy, where everything is dictated by the leaders - what and where to farm, how much to produce etc. I think 80-90% percent is a safe percentage for mundane/wizard population ratio. So you'll need 8-10 people for each wizard in order to support them.

Going off some of the threads you provided, I'd suggest somewhere between 100-150 for your flying island. This will be pretty bare bones - most will be occupied with farming, fishing and maintenance. People will do double-duty to fulfil whatever trades as required. As you increase the population, people can start to specialise, with distinct trades and actual merchants, rather than just selling excess produce.

As an example of tiny self-sustaining colony, I'd like to point out Pitcairn Island. Founded by the mutineers from the Bounty, they've been a tiny colony in the middle of the pacific, ranging in population from ~30 to a peak of 250.


It is not an island. It is a tree.

The great tree floats onwards over the sea, its roots skimming the surface. Sometimes it floats high into the sky, much to the chagrin of the fishermen who make their homes among its roots. Sometimes it descends so deep that the trunk leaves a wake behind it. The tree alone knows its reasons.

Among and within the branches live the people. The tree provides wood, fruit and shelter. Chickens and iguanas live among its branches. Other rarely seen creatures forage in the unpopulated expanses of the distant leaves. Expeditions to the crown can retrieve the strange leavings of lightning and fallen stars.

With the flying tree as your basis, your community can be as large or as small as you like. Your story can determine your needs. There can be a man and a woman, living on opposite sides of the tree. There can be a village of hundreds.

  • $\begingroup$ Neither do I understand why it should fly using magic when it can float using physics. $\endgroup$
    – user35577
    Jul 1, 2018 at 21:40
  • $\begingroup$ @qqjkztd Rule of Cool flying Islands are cool, plus A Wizard Did It so it doesn't have to make sense. $\endgroup$
    – Ash
    Jul 3, 2018 at 13:28

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