Let's say there is an underwater civilization of merpeople. They were able to develop medieval technology (approximately, since an underwater civilization would develop differently than an above water civilization). They were also able to build a self-sustaining, large city with several houses. How would the city be structured?

Details about the merpeople:

  1. They can breathe both underwater and on land, but depend on water, kind of like amphibians. They can remain outside water for an hour, at most. They could also travel on land but are not fast.
  2. Can trade with nearby people that live along the shoreline (also medieval technology). So they have access to above water resources and tools, but not very much.
  3. Have decent night vision. But they prefer being in a bright environment. They can't use echolocation.
  4. Don't have enemies inside water. There are no other merpeople. The only threats are above water civilizations and underwater creatures.
  5. Farm seaweed and cultivate fish for food. They have plenty of food, so they have leftover people for craftsmanship, architecture, and resource-gathering.
  6. Have a population of several thousand people (around 5,000).
  7. Live pretty close to land. The closest shore is about a 40 minutes swim.
  8. Lives on or close to a coral reef. So on shallow areas of an ocean.
  9. Will be building the houses out of coral.

I'm trying to draw some concept art of this city (bird's eye perspective).

To be more specific about the question, structure as in, how would the city look like from a bird's eye perspective? Will there be any key features that stand out (palaces, walls, marketplaces, houses)?

  • $\begingroup$ You are asking a lot of questions in this post. We have a strict one question per post policy. Please edit this post so that you're asking one specific question. $\endgroup$
    – sphennings
    Commented Oct 17, 2021 at 3:20
  • $\begingroup$ @sphennings The considerations are just considerations and are not essential. People can only answer one of them, or just give me a vague idea of how the city would look like. $\endgroup$ Commented Oct 17, 2021 at 3:23
  • $\begingroup$ @sphennings But I edited the question to make it only a structure-based question, just in case. $\endgroup$ Commented Oct 17, 2021 at 3:33
  • $\begingroup$ I think that the question, as edited now, is clear enough to address - it wants to know how a merfolk city would be organized. $\endgroup$ Commented Oct 17, 2021 at 5:16
  • 1
    $\begingroup$ As is this is still asking for a book not a straightforward answer. $\endgroup$
    – Ash
    Commented Oct 17, 2021 at 7:54

2 Answers 2


To start off, there are common things that you need in all cities - there is a reason why they exist. They started off as being hubs for trade, and so you would probably want some kind of market in the city. If you do not have a market or commercial district in the city, you need a pretty good reason for omitting it, as that it is big reason to live in a city.

A further mark of all cities is that you need something to support it. That means you probably want a considerable amount of room to produce food. If the seaweed is a primary food source, or the fish need some kind of extensive room to be raised in, you want to make that a big thing surrounding your city.

Cities, historically, have also been very advantageous because they provide safety. However, if your merfolk do not have any large, coordinated enemies, the most you would probably need is squads of merfolk watching to ensure that seaweed farmers are not attacked by sharks.

Merfolk cities introduce a number of problems though, and it changes depending on how realistic you want to go. If the merpeople can't withstand high pressures they would probably stick to coastlines and in freshwater areas, same for if they don't hand the darkness of the ocean well.

In a mer city, you also have considerations like streets. If the merpeople can essentially "fly" over everything, then the need for streets may not be as important. However, you might consider the route that I've taken in my merfolk cities - merpeople do not like strangers just swimming over their houses - plus, it helps to have things organized in some manner so that you can find things. In places where you're up against rock outcroppings, or in ravines, you might find merfolk homes or businesses crammed everywhere they can fit, as being able to swim to any height allows for this.

Merfolk cities, as I said, can be complex, and the needed structure will change depending on what exactly you want your merfolk to be like. You do have underlying principles of cities, like I mentioned, and there are many more, that you might research to give some plausibility. Other than that, your city structure will fluctuate tremendously depending on the city's purpose (ie, is it civilian, military, a government seat, a religious site?) and merfolk traits.

One word of advice for making organic growth - do some basic plotting out of how the city would grow initially, making up a bit of a history for each stage of growth. Perhaps you might start out with them kind of just using the coral as shelter. Then they build in-between the coral. Then they are able to chisel into the coral structures. Trade gives them access to tools that can build new underwater buildings, and get rid of the coral, and so you see pock marks in the city of newer buildings where coral once was, surrounded by older buildings that had to be built around the coral.

Things like that can help a lot.

  • $\begingroup$ +1 for the comment about plotting. If the city wasn’t rigorously planned beforehand then doing quick sketches of it at each stage of development (including legacy features from the sketch before) helps even if you ignore the idea of ‘streets’, since you’ll be able to see where you have to leave gaps so your merfolk can get to the market/townhall/amphitheater/farms etc. $\endgroup$
    – Joe Bloggs
    Commented Oct 17, 2021 at 10:50
  • $\begingroup$ @JoeBloggs Besides, it's helpful to consider - if this is a city, and there's large amounts of merpeople moving around, it would STILL be helpful to have things organized into streets. Having everyone swimming all over the place would make things very disorganized. Perhaps it could be considered "jayswimming" xD An idea I'm intrigued by is vertical streets. If the city was sufficiently big enough, they might actually be building enough tall buildings together where you'd enter a building by swimming up to it. $\endgroup$ Commented Oct 17, 2021 at 19:37
  • $\begingroup$ Vertical streets would be a necessity for high density buildings, since you’ll still need a way for people to enter/exit the ‘ground level’ streets without needing to go to the edge of the city. Might make more sense to have them as chasms between buildings and have traffic flowing in alternate directions in vertical lanes. In either case a sketch of the city can show where you need entry/egress points as new buildings overtake old infrastructure! $\endgroup$
    – Joe Bloggs
    Commented Oct 17, 2021 at 20:01

A common characteristic of most cities pre-1800, that might carry underwater too:

The rich folks tend to live upstream (where the clean water is).

The poor folks tend to live downstream (where the polluted water is).

  • $\begingroup$ And if follows when it comes to other problems too - perhaps in this part of the ocean, ocean storms can be bad, and so all the wealthier housing is closer into protected areas, so the poor have a higher chance of having their homes destroyed. $\endgroup$ Commented Oct 17, 2021 at 19:38

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