I've got a species that lives in the Southern Ocean along the Antarctic coast, and they are basically a sentient crossbreed of Orca whales and elephant seals. They are omnivores, have opposeable thumbs, a level of technology comparable with our own, and have lived in the same place for many centuries, at a depth of a couple hundred meters on the sea floor. They are mammals and breathe air, but sleep for very short periods so I don't think their houses all need to be filled with air, per se. They are definitely not living under domes.

What would their cities look like? I have looked at construction materials from this question, and settled with quarried stone as their primary material.

I initially thought to make the city very tall and multi-levelled, with the highest levels reserved for hydroponic farms, but if you build tall towers then the currents may push them over, so I'm guessing that's not ideal.

What sorts of city lay-out would you get with a species that lives in the water? E.g., would their doors be on the top of their houses?

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    $\begingroup$ how can a water dwelling civilization have our level of technology if they cannot use fire, which is how our technology started? $\endgroup$
    – L.Dutch
    Jan 13, 2019 at 9:59
  • $\begingroup$ Please clarify some things: why do they build a city? What is in that city? Where do they build it? Do they design it from scratch or are there historic buildings? How do your animals move around? Where do they need to go? How do they eat? What about money?Is space a limitation? Do they care about how their city looks (don'tsay of course unless you've seen what the communists and post war Germany did to their cities)? And what possible advantage could a house have underwater? That's kind of my first question again, but well, people here don't ask the why question enough. $\endgroup$
    – Raditz_35
    Jan 13, 2019 at 10:03
  • $\begingroup$ @L.Dutch They don't have fire. Their technological advantage is farming. An elephant seal spends 90% of its day hunting for food - these guys are intelligent enough to farm their food, so they have a lot of free time for civilisation building and technology. $\endgroup$
    – KeizerHarm
    Jan 13, 2019 at 10:06
  • $\begingroup$ @Raditz_35 Uh... I answered most of those in my question, actually ^^; It is built on the ocean floor near the Antarctic coast, at a couple hundred meters below the surface. It is a multi-century old city. They farm their food. I can't see how money is relevant to city architecture. Space is no limitation. I think they would at least use houses for storage of personal belongings. And aesthetics is no concern for my question, all I care about is whether they would have roads and what form their doors would be, etc. $\endgroup$
    – KeizerHarm
    Jan 13, 2019 at 10:08
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    $\begingroup$ Air breathing mammals would not live "at a depth of a couple hundred meters" because they would need to spend more time at the surface to breathe than in their city. Giving birth at this depth would be lethal if you don't have air supply for the infant. $\endgroup$
    – Elmy
    Jan 13, 2019 at 18:47

2 Answers 2


Marine mammals can stay underwater for 10 mins to 2 hours tops. This is fantastic compared to humans, but not enough to justify an underwater city. Underwater storage units maybe.

Your species is a cross between elephant seals and orcas. The former holds the underwater record: 2 hours (though the Curvier beaked whale broke the record in 2014 with 2:17). For orcas, it's more like 15 minutes.

Your city would have to be a mixture of above and below water.

I imagine stone walls rising several feet above sea level, completely enclosing a space. Multiple such spaces around the city, each the size of a swimming pool, though some larger or smaller spaces might be useful. Underneath the water are places for storage and private meetings. Fish farms and gardens exist both open to the air or not, depending on the species cultivated.

To enter or exit any given unit, you would go underwater to passageways that take you in and out of the city and/or to other units. This is to minimize intruders. Only good swimmers can make it. Anyone not brought up in the city (or guided by someone) is liable to get lost and drown. It's not possible to jump the walls. While some land animals might be able to climb them, they'd have to get there first.

A couple hundred meters is a very long way and walls that anchor in the bedrock aren't likely at this distance. So the city would need to be in more shallow waters or at least on top of a shelf or other natural structure that makes the water more shallow in one area, even if it is surrounded by deeper waters (easy enough to find if you're close to the coasts, as most marine mammals are).

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    $\begingroup$ Oh boy, I have some rethinking to do... Thanks for the big heads-up! :D $\endgroup$
    – KeizerHarm
    Jan 13, 2019 at 21:48
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    $\begingroup$ @KeizerHarm Something like this might give you both. researchgate.net/figure/… $\endgroup$
    – Cyn
    Jan 13, 2019 at 22:03
  • $\begingroup$ I just got to figure out a reason for why they were not detected until modern day... We do not know much about the seabed, but plenty of ships have circled Antarctica and they never stumbled upon a half-submerged city. $\endgroup$
    – KeizerHarm
    Jan 13, 2019 at 22:29
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    $\begingroup$ Make that a different question. Right now you're talking about architecture. And keep in mind that ships avoid shallow areas and they're well marked on ocean maps. If the location were in the middle of multiple sets of shelves, it's possible no one has seen it yet. $\endgroup$
    – Cyn
    Jan 14, 2019 at 1:05
  • $\begingroup$ Yeah, I was just rambling. Thanks, in any case! $\endgroup$
    – KeizerHarm
    Jan 14, 2019 at 12:48

Building design

The roofs would be angled till they touched the ground because the high pressure would otherwise require ridiculously big walls and stone slabs the same size as the roof. If they are able to build non only roof buildings the buildings would be as high as possible pressure would decrease with height. Height would also depend on the strength of currents.

No pressure concern

Buildings would probably be built like they are in out world. Although still higher if travel speeds are a concern other wise houses would not take any significant changes. (except for adjusting rooms and door ways to fit their inhabitants)

Doors would definitely be to the sides. (on top would mean to much pressure) What also could be a design is that all buildings are carved out of an underwater cliff.


Because they can use vertical design roads can be much thiner they can just move upwards or downwards to avoid collisions.

Layout of the city would depend on how fast they are able to move through water if they are as fast as we walk they would localize every aspect as much as possible (shops/food/jobs/public areas close and decentralized also dentists would be spread out so that everyone can reach them as fast as possible) the more the speed equals our cars the more the city design would centralize and all jobs would move to the city center and so on.

  • $\begingroup$ Hmm, and what if pressure were no concern? Such as if only a few of the buildings were filled with air... $\endgroup$
    – KeizerHarm
    Jan 13, 2019 at 13:41
  • $\begingroup$ Why would pressure matter? Internal and external pressure would be equal, unless for some reason they used pumps to reduce the pressure inside the buildings. Doors would have to be on the underside for air filled buildings, or the air would escape. $\endgroup$
    – user42528
    Jan 13, 2019 at 20:04
  • $\begingroup$ @KeizerHarm I added a section for that. $\endgroup$
    – Soan
    Jan 13, 2019 at 21:44

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