Subterranian City Planning

[madcowchef]

A lot of fantasy has entire large populations living underground. Assuming basic things that every city needs (rivers for water and sanitation) and appropriately fantastic geology (enough massive cave systems to be populated by huge numbers of these peoples) how do you think such a city would look on the small scale? Alleys and courtyards seem out as they appear under normal conditions when a back lot gets boxed in, and the extra effort of moving dirt for many buildings means that more planning in general will probably go into these cities and they seem more likely to be compact to me. What other details should and would be different? I'm interested in people thoughts on this.

[Wingshaw]

This is an interesting question. I'll have to give it some proper thought. The first thing that occurs to me is that the settlement could expand vertically just as easily, or moreso, than horizontally. You might be interested in this picture, of an underground city in Cappadocia, Turkey.

I think you may be wrong about the town needing more planning, though. The amount of planning a settlement receives is generally a product of the level of government or central authority, not the circumstances of the town.

[Raptori]

Very interesting question, pardon me if I write a short essay

From what I've read, a lot of really basic stuff is overlooked in an underground setting. Roughly speaking, the five basic needs of life are: food, water, oxygen, living space, and appropriate temperature. I've yet to see an underground culture developed that really accounts for all five of those (though to be honest it's rare to see them fully developed, and there's a good chance I've missed some that do consider that kind of thing). It'd make sense to at least consider how those five things would influence the way the city would develop, since they really are important.

(Note: the below is based on the few underground civilisations I've encountered, hopefully someone can point to some that actually do account for these, since that'd be well thought out fantasy that I'd like to read!)

Food
Most of the time the food source isn't even considered, even in the case of your typical dwarves shunning everyone else and living deep underground. They often seem to eat a lot of meat - where does it come from? Do they have the equivalent of underground factory farms (since space would be at a premium)? Where do they get the feed from? Where do they get their own vegetables, since pseudohumans presumably need the same nutrients humans do in real life, which cannot be provided by meat alone. Do they farm fungi (and if so, what do the fungi consume)? If all food is brought in/traded from outside, then can it truly be considered an underground civilisation rather than an outpost of a larger civilisation?

Water
This the easiest to account for thanks to underground rivers, though it'd also be nice to also see references to rainwater filtered through the rocks. Water collectors built underneath stalactites would be a pretty cool detail. You could also cut wells down to the water table.

Oxygen
Another one that doesn't seem to be considered, there really does need to be some reliable ventilation. This bit reminds me of ants and termites - they create brilliant ventilation systems to manage the oxygen and carbon dioxide levels so both they and their farmed fungi can survive indefinitely. You'd have to design your architecture so that the air can flow through properly, circulating the air and keeping it fresh. Some modern buildings do this passively, so they'd be a good place to start looking at to see how this could be done.

Living Space
As you said, this could be planned out in advance, particularly because weakening the structure of one area could bring the whole thing down. It'd make sense for the plan to be constructed in stages, with various sections being planned well in advance and then excavated when the extra capacity is needed. However it could still be grown as per normal cities - and then you'd be able to add a third dimension to the growth, allowing connected infrastructure to cluster together more closely. I think the routes goods travel would be influenced by that - carrying heavy stuff upstairs all the time would be a nightmare, so a well organised city would arrange things so that goods tended to travel downhill or stay on the same level.

Temperature
Another thing that's often ignored - beyond the influence of the sun it's cold, until you get reeeally far down. If you're using big fires to keep the temperature up, where does the fuel come from, and how do you deal with the smoke?

The obvious solution to all of those problems is magic, but I think that would be kinda lame...

[Gamerprinter]

Food
Most of the time the food source isn't even considered, even in the case of your typical dwarves shunning everyone else and living deep underground. They often seem to eat a lot of meat - where does it come from? Do they have the equivalent of underground factory farms (since space would be at a premium)? Where do they get the feed from? Where do they get their own vegetables, since pseudohumans presumably need the same nutrients humans do in real life, which cannot be provided by meat alone. Do they farm fungi (and if so, what do the fungi consume)? If all food is brought in/traded from outside, then can it truly be considered an underground civilisation rather than an outpost of a larger civilisation?

I cannot claim that every underground city map has effectively shown it's source of food, but I can remember the boxed set to city of Menzobarrenzan, the Drow of the Underdark, where the map depicted an area about a fifth of the size of the entire city chamber as holding an underground lake, islets, fungus fields, even underground cattle raised there. Realistically there probably was need for a larger more extensive area to serve as farms to adequetely feed the city, but it did exist on the map. Often there is a nearby underground sea or lake that might serve as the primary source of food as in fish, and might be very close, but not an actual part of the underground city map in of itself.

Water
This the easiest to account for thanks to underground rivers, though it'd also be nice to also see references to rainwater filtered through the rocks. Water collectors built underneath stalactites would be a pretty cool detail. You could also cut wells down to the water table.

There are probably dry cave systems in the underdark as well, but if there is no water source, then there is no city. I would believe any underground city requires underground cities, great aquifers, underground lakes, even collected water dripping from the ceiling of caves. Most underground city maps feature a river or lake within the community borders.

Oxygen
Another one that doesn't seem to be considered, there really does need to be some reliable ventilation. This bit reminds me of ants and termites - they create brilliant ventilation systems to manage the oxygen and carbon dioxide levels so both they and their farmed fungi can survive indefinitely. You'd have to design your architecture so that the air can flow through properly, circulating the air and keeping it fresh. Some modern buildings do this passively, so they'd be a good place to start looking at to see how this could be done.

I've never seen air ducts accessing the surface for most underground cities, and though this might not seem realistic, for reasons of safety, only one or a few entrances are even wanted for access to an underground city for the sake of defense. Most underground cities aren't near the surface, so any air ducts would probably have to be very deep, and if they are straight verticle ducts their existence might prove to offer unnecessary access to the city. Also, one would have to believe that an actual underground race should be biologically adapted to working in an environment with lowered oxygen levels. If its a surface race that has moved underground, they will certainly need some type of air duct system. If its an underdark race, I have to assume they are adapted to live and operate in lower oxygen levels, or increased levels of carbon dioxide and other gases. Not all races might need an air filteration system to survive in the Underdark.

Living Space
As you said, this could be planned out in advance, particularly because weakening the structure of one area could bring the whole thing down. It'd make sense for the plan to be constructed in stages, with various sections being planned well in advance and then excavated when the extra capacity is needed. However it could still be grown as per normal cities - and then you'd be able to add a third dimension to the growth, allowing connected infrastructure to cluster together more closely. I think the routes goods travel would be influenced by that - carrying heavy stuff upstairs all the time would be a nightmare, so a well organised city would arrange things so that goods tended to travel downhill or stay on the same level.

Looking at Menzobarrenzan again, many of the drow house 'castles' were rock-cut chambers cut from existing giant stalagtites and stalagmites, also many were typical stone and mortar constructed buildings like any surface city. Anywhere that exists a verticle surface in the walls of an underground chamber are regions of mostly solid rock, thus rock cut chambers, tunnel systems (like those in Cappodocia) would probably be prevalent. Even a wide pit that drops some distance in the floor of a cave, could serve as a 'skyscraper' going down, with levels, chambers, tunnels, even bridges across the pit, connecting to the lairs that surround the pit in the walls of solid rock. It might even be possible to build wood-like surface structures from the 'timbers of giant fungus'.

And with large enough chambers, I don't see why an underground city might not actually resemble a surface city with roads, alleys, enclosed yards, market squares and rows of constructed buildings. There are literally enormous open chambers found in Mammoth Caves, Carlsbad Caverns and other actual underground cavern systems on Earth. There's no reason why a surface looking city could not exist underground.

Temperature
Another thing that's often ignored - beyond the influence of the sun it's cold, until you get reeeally far down. If you're using big fires to keep the temperature up, where does the fuel come from, and how do you deal with the smoke?

The obvious solution to all of those problems is magic, but I think that would be kinda lame...

The first thousand feet under the surface the ambient temperature is fairly constant at 50 - 55 degrees F, though this varies in depth. As long as there is some internal heat source in homes and structures, this temperature range is survivable for most surface/underground sentient races. However, even without nearby magma chambers, volcanic channels, steam vents or geyser aquifers, you don't really have to go to far down to find the temperatures rising. Deep mines even those from as far back as the medieval period were found to be warmer in the lowest levels. I've read National Geographic articles regarding the diamond mines in South Africa, and at the lowest levels of the mine, it is almost too hot for humans to work in (and its not even a mile deep). So though the earth's core might be hundreds of miles down, you don't even need to get close to that to find hot temperatures underground. Even if a city resides above the warm layers, it would be probably be more practical to dig air ducts down to the warm levels circulating into the inhabited chamber (than digging air ducts to the surface.)

Nobody builds a surface city where there are no resources to support it. So I wouldn't think an underground city would appear anywhere there is an open space underground, if the supporting resources aren't there, neither is any population. There needs to be the basic resources to support life at any location for a city to be founded.

[madcowchef]

Excellent point about the planning THW. From what I've read of some human cultures even let alone fantasy ones there are plenty of places that even if your poor planning collapses your home or a neighbors that's just the way of things and no government or higher degree of planning may be present. Perhaps my thinking was overly tainted by the traditional view of orderly dwarves.

Food source has always been an interesting one to me in particular. Ultimately (with the exception of geothermal vents which would be a fun option to explore) the sun provides the energy for all ecosystems. The only large influx of outside nutrients I can see coming into a cave system (unless you create one like underground migration routes for some large land animal, another fun option) is that which can be carried by an underground river. So fishing would be important. From several accounts I've read villages tend to poison their own creeks once they grow too big which causes a die off of the fish. With a big enough river you can't put enough waste in it as easily, so you'll need a large underground river. If you are going to do the fungus, as you point out, you'll need food for fungus. You could maybe modify a system with bat's bringing in enough of the right kind of waste (the actual guano is pretty nasty stuff though mixed with other things is some killer fertilizer) or some other imaginary animal. In some ways though this problem is common to all large cities none of which can produce enough food without outlying lands.

As far as temperature goes, it might not be warm, but it is very constant and there is no real change in season or the like so if your body as well as culture developed there you are living the easy life as far as adaptation. This seems like it would also have an effect on buildings as what weather is there really to keep out?

[Raptori]

Good point about fishing, I hadn't thought of that. I wonder if there's anywhere in real life with an underground fish population large enough to sustain a human population... Also, insects like this ridiculously disgusting thing would most likely also be staples of their diet, particularly if they have lots of bat guano. I like the idea of a big underground lake containing geothermal vents, sounds really unusual

Mm yeah, buildings would most likely be very open plan, without as many dividers as you see irl I guess

[madcowchef]

Bugs: natures snack food. The river would work best if it ultimate came from the surface rather than originating under the ground. That way its bringing nutrients and fish into the system rather than just some poor pale little cave fish. Though maybe you could make some fantasy salmon that lay their eggs in cave systems to protect their young rather than bothering with open streams.

[Wingshaw]

Well, to deal with each of Raptori's points:

Food:
Food is only going to be a problem if your underground dwellers are completely cut off from the surface. The traditional dwarven mining stereotype assumes that the wealth produced from within the earth (in the form of metals and jewels) is more than enough to buy all the food necessary. I think that this is the most probable scenario (the beginning of the first Hobbit film displays this possibility very effectively).

I do think that there is room for some imaginative problem solving, here, though. My knowledge of biology is poor to terrible, but I'm sure there are types of algae or simple organisms that can exist underground. I've heard that life on Earth may have originated deep in the oceans, around volcanic wells. If this is true, sunlight is not needed, but minerals/nutrients (and warmth?) are important. These could be found underground. I am now imagining the residents of this city tending large 'fields' full of a disgusting white soupy substance.

Water:
I think Raptori covered this one pretty well. If you refer to the image I linked to before, you'll see that the Cappadocians dug wells into the water table.

Oxygen:
once again, I agree with Raptori's assessment. Ventilation will be necessary, and ants and termites can provide decent models for that ventilation. Generally, I would recommend a city with a tree-like shape: large thoroughfares with smaller ones coming off them, and then smaller ones and so forth. That way foul air can be flushed out easily enough. Another important thing would be some kind of cross-breeze effect (if the city is inside a hill or mountain, it could have an opening on the windward side, and another on the lee side), which would provide the operation of removing the bad air, while bringing fresh air inside. If the city is located underneath, say, a desert or plain, air could be a problem.

Living space:
I disagree with Raptori that space would be at a premium. Underground, you have far more space than above ground, especially when you factor in the ability to develop vertically as well as horizontally. I foresee two issues when expanding this city: I) encountering hard rock that is too difficult to dig through, and II) risking an area collapsing. The first could thwart any preconceived plans that you develop, and would probably result in a city that evolves with solid patches where the diggers could go no further.

The second would not be too difficult to deal with either, at least partially: you would most likely be naturally inclined to leave walls more solid than necessary as part of the process of excavation. Adding plenty of supporting structures (timber--traded, obviously--or metal being the most useful). Collapses can still take place, but they might be regarded as a worthwhile hazard. Consider, for example: making houses (and even streets) out of wood in medieval Novgorod (which, being such a cold climate, would also necessitate plenty of fires for warmth). In Australia each year, bushfires and floods wreak havoc, but we still rebuild. I think this hypothetical underground city would be the same: if the advantage of living underground is big enough (eg vast seams of gold, protection from ravaging hordes or plagues), people will risk partial cave collapse.

Temperature:
I think I remember hearing that, in architectural history terms, living underground makes a lot more sense from the point of view of temperature. In cold climates, the insulation would keep the town warm (relative to the surface temperature), and in hot climates it would keep the temperature low. All year round, as MCC says, it would keep the temp stable.

Some other thoughts:
I don't think houses would necessarily be open-plan. It would help with the ventilation, but would weaken the supports holding up the roof. Here is what I think would be sensible architectural features for this city:
-front doors might be nothing more than metal bars in a door frame (provides security, without blocking the fresh air). The front room in historic cities often contained only a shop, workshop or lobby anyway, and so privacy isn't going to be an issue (and curtains can be used to provide privacy through those doors). Sound also won't be a problem due to the thickness of walls.
-as much as possible, ventilation will be built into the design: internal doorways will be very large, and perhaps have no doors or gates; rooms will try to have direct access to the thoroughfares.

Raptori's point about moving objects up stairs is easily dealt with. It wouldn't be too difficult to excavate vertical shafts and have pulleys to move heavy goods (and possibly people). The labour of moving all of this earth would be minimised by the incremental way it is done (a lot of labour goes into building a house, but I will hazard a guess that it is probably about the same amount of labour needed to dig a house).

Planning: sorry to harp on about this, but, as a qualified urban planner (and an unqualified urban historian) I do not think that this city would need planning. It is, as I said before, determined by the nature of government. If the city has a totalitarian leader, he/she might want a specific design, but if this city has grown out of a peoples' necessity, and emerged over decades or centuries, it would grow spontaneously. And the result would be areas that are badly made: ventilation might not be included in the beginning, and so they would enlarge their tunnels when new people arrive (or people begin to asphyxiate); enlarging those tunnels may involve filling in some peoples' homes, or creating a new thoroughfare, where all the richer people move to.

Well, this turned into quite a long post, so I'll leave it there for now.

THW

[Raptori]

Very good points THW

Living space:
I disagree with Raptori that space would be at a premium. Underground, you have far more space than above ground, especially when you factor in the ability to develop vertically as well as horizontally.

I was assuming a slow excavation rate; thinking about it that would make no sense at all in this situation!

Temperature:
I think I remember hearing that, in architectural history terms, living underground makes a lot more sense from the point of view of temperature. In cold climates, the insulation would keep the town warm (relative to the surface temperature), and in hot climates it would keep the temperature low. All year round, as MCC says, it would keep the temp stable.

Not 100% sure, but I think that principle was applied mostly to moderately buried houses (like hobbit holes) rather than deep in the core of a mountain - though it stands to reason that it should be roughly similar. The rock would act as an effective heat sink, so once you've got it warmed up initially it should be quite easy to keep a good temperature once it's warm enough.

Some other thoughts:
I don't think houses would necessarily be open-plan. It would help with the ventilation, but would weaken the supports holding up the roof. Here is what I think would be sensible architectural features for this city:
-front doors might be nothing more than metal bars in a door frame (provides security, without blocking the fresh air). The front room in historic cities often contained only a shop, workshop or lobby anyway, and so privacy isn't going to be an issue (and curtains can be used to provide privacy through those doors). Sound also won't be a problem due to the thickness of walls.
-as much as possible, ventilation will be built into the design: internal doorways will be very large, and perhaps have no doors or gates; rooms will try to have direct access to the thoroughfares.

Yeah with that bit I was thinking along the lines of the sietch communities in Dune... what you said makes a lot more sense given that we're probably talking more active excavation in this case.


I like long posts

[madcowchef]

All excellent points! I remember reading stories of collapses of whole multistory tenements in Rome being common (which isn't to say people didn't get mad about it). It make me suspect we are too immersed in modern thinking in regards to planning. People got by (albeit with shorter lives and poorer living conditions) with little or no real planning at all for most of history so I can see your point there. Biologically speaking you have two forms of autotroph photo and chemo (sun users or chemical users like the ones you get at thermal vents) everything else lives off of these ultimately. Of the two chemo is comparatively rare, but a big underground vent system with animals and fungus that feed off of the vent feeders would at least be very interesting and fun. Thanks for all the insights.