Assume there is a medieval city with 100 million souls inside. Let's ignore the questions why they wanted to build such a city.

In next given conditions, could this city be possible?

  1. the world follows basic physics rule.

  2. There is a magic that enables construction of building with a maximum height of 1,600 meters and underground 500 meters. (And I mean construction, not maintaining)
    The Magic might be the knowledge how to build the city and a plan for the city

  3. The city should be built with pre-17th century technologies.

  4. Unlimited workers and resources provided.

  5. Yes, there should be infrastructures like water supply, market, harbor, etc.
    (Please don't say things like Build human wall or Build a house with gold coins kind of stuff.)


I mean possible within the meaning of maintenance of buildings and the city itself. I don't care about Law and Order or if half of city just die within a year.

The city will be enclosed by a wall, and its size should be less than 8,000 square kilometers.


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    $\begingroup$ Is it a medieval city because it is enclosed by a wall? How much land would it cover? All of California is a population of 38 million. You'd need a phenomenal amount of farm land to support 100 million urban people. $\endgroup$ – Mazel Jun 10 '17 at 6:19
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    $\begingroup$ That is not a medieval city. Medieval cities don't have buildings one mile tall. 100 million is more than the entire population of Europe during the Middle Ages. During the High Middle Ages (11th to 13th century) Europe had 60 to 70 million people. At that time the largest medieval European city was Constantinople which had some 200 to 300 thousand inhabitants. P.S. "Magic" is not a "pre-17th century" construction technology. Either you have magic or you have medival construction tech; they are not the same. $\endgroup$ – AlexP Jun 10 '17 at 7:26
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    $\begingroup$ the statement there is magic that enables construction of building with maximun height of 1,600 meters... goes against the next statement of using only pre 17 century tech. If something allows you to build such buildings, like magic, why would you use technology that gets 150 meters at its best? $\endgroup$ – Emilio Liaño Jun 10 '17 at 7:35
  • $\begingroup$ According to economic theory unlimited money and workers is not realistic. USSR tried to achieve a state where resources are abundant during all its 80 years of existence so people would not need money. After 80 years they had less resources than countries that never tried to achieve unlimited resources (USA, West Europe) $\endgroup$ – keiv.fly Jun 10 '17 at 12:05
  • $\begingroup$ As @EmilioLiaño notices height will be the main problem, because of materials and technologies limitations. With 10 story buildings (about 30m height) they can host about 30 million people on the territory (8000km) - based on some of the current cities. Those buildings can be built with 17-th cent tech. (materials bricks and cement). So you really do not need building that high - but if it is the requirements they are 1600m height (and not up to 1600m height) - hm, is the brilliant bricks supplier included? $\endgroup$ – MolbOrg Jun 10 '17 at 12:52

One of the most important limiting factors for the size of cities is the amount of food that can be produced. Aztec city Tenochtitlan used very advanced agriculture method chinampas and achieved the population of the biggest cities in Europe at that time (200 thousand people). In years before 1900 even after industrial revolution most of the population of Europe was still employed in agriculture. Currently the biggest aglomeration is Tokyo with 37 Mln people. So even now 100 Mln is on the limit of current technologies.

There are also other technologies that limit the population:

  1. Fresh water
  2. Medicine (disease is spread faster in cities)
  3. Transportation (you cannot go to work of the trip to work lasts more than 3 hours)

There are probably other technological limitations.

So the answer whether the city is possible depends on the strength of magic. Without magic a medieval city of 100 Mln people is not possible.

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    $\begingroup$ ...Also sewage removal.. $\endgroup$ – nzaman Jun 10 '17 at 11:51
  • $\begingroup$ "Currently the biggest aglomeration is Tokyo with 37 Mln people. So even now 100 Mln is on the limit of current technologies." - there not a lot of countries which population is above 100 million people and usually they have enough territory and no incentive to concentrate the population in one place. So, I would not say that 37 is the limit for our technology. It definitely can be used as an example of the biggest city, but it is not the limit. $\endgroup$ – MolbOrg Jun 10 '17 at 12:17
  • $\begingroup$ You are right that now 37 Mln is not really limited with current tech and the food is less limiting now than it was before. But I heard that in Tokyo people have very little flats that are extremely expensive and they feel that the city is crowded and they are unhappy about it. So I think with 100 Mln people it would be extremely crowded. $\endgroup$ – keiv.fly Jun 10 '17 at 12:28
  • $\begingroup$ As OP is not caring about the happiness of those people it's not a concern. $\endgroup$ – MolbOrg Jun 10 '17 at 12:56

Yes, it would probably be possible.

Apart from food issues, the magic would clear the rest. I think in a scenario, where you can build such superstructures, they might even be held together by that magic.

And even issues like feeding everybody might not make a huge difference, as the infrastructure (especially the harbor) could be so big that the city just buys everything as they have unlimited amounts of money.

So all in all: A city like that would be possible, although every structure would be held together using magic.

PS: By the way, even the money problem could be (at least partially) solved if the city was some kind of giant marketplace with high taxes.


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