The Practicality of a "Moria-Like" City

[Crossroads Inc.]

SO real quick.. I use the word "Moria-Like" because I want to discus the concept of the underground city.. but not its Size (lets be honest, Moria is Stupid Crazy Big)


OK... So the concept of the "Underground mountain city" is one repeated many times in different fantasy worlds.
We see it a lot in LotR, WoW, DnD etc...
But... How Practical is such a concept?

With modern construction methods of course, we have underground facilities..
but a full on "City"...

Well Mines in general tend to be cold, damp, and dangerous places. The notion of taking such a setting and making it a place for people to Live in is while "romantic" but how feasible is it? Excluding the direct use of "Magic" If you were to have a community of... Oh, lets say just 1,000 people...
You would have say
School,
Hospital
theater
Library
Food Storage
Living spaces
communal spaces
Shops
Waster storage and Waste treatment..

All of that within a mountain... For our purposes, this isn't some sealed vault, so food and supplies and trade from outside is perfectly normal..

So,.. What would be needed to ensure, not just a Safe facility, but a comfortable one as well? Keeping it Warm in winter, cool in summer, Keeping it well lit etc? In a Standard fantasy setting WITHOUT Magic... Would such a place even be practical?

[Formless]

How deep does it have to be dug to be considered "Moria-like"? Because there are real life underground cities, including ancient sites like Cappadocia in Turkey that you can use as a template.

[Lord Revan]

There's examples of pre-modern cities built into cliffs and what not.

First thing to consider is how much of the caverns are actually built and much of it is repurposing natural formations, Moria (from LOTR), Ironforge, Grim Batol and the Blackrock mountain settlement(s) (from WoW) were built inside semi dormant volcanos at using at least partially the naturally existing caverns only expanding and re-enforcing those.

and with at least Moria IIRC it was pretty outright stated that there were tunnels built into the mountain to allow light and air to the city itself.

If you had the means to build such a place it would be the ultimate fortified citadel as the mountain would act as your city walls.

[Zixinus]

Building an underground city is rather massively expensive (all the cost of building a regular city + all the problems of underground construction) but not impossible, barring favorable geological circumstances (this is the key point really) and providing the logistics for air circulation, water, sewage, etc. Especially if you include industrial-level or higher fantasy civilizations that have access to power tools, pumps and such.

A quick search shows that there have been cities that could accommodate as much as you mention and more. Again, once you have the critical thing (air and water) going in and out, it is quite possible to build underground cities. Actual fallout shelters/bunkers and such have been designed to last as complete mini-cities for a long time. Some were built in old salt mines and such, into existing system of caverns.

In terms of practically, as others noted, it would be very good. By building into the mountain wall, you create natural denial of attacking zones (imagine having to build a fortress in an open plain where you can be attacked from multiple sides). Tunneling into the mountain is not an easy undertaking at peace time and is an avenue where the defenders can strike back, due to tunneling requiring bottlenecks. And if they are losing that or the enemies find the defender's, they can always cave those in.

[Sea Skimmer]

Moria like just isn't practical without either enormous caves ventilated by natural draft, which would provide little defensive advantage for the trouble to build them, or at least having steam engine technology for ventilation. And really you need electrical power and natural gas, because otherwise all cooking and lighting is poisoning the air with carbon monoxide. That may not be a deal breaker for a short term shelter, but its a huge issue for a city with industries.

Merely sheltering a population for a few weeks or even all winter long is way easier as a goal.

The point of such a city is also open to question unless its to protect against large monsters, since if the enemy merely seizes control of the air intakes on the surface they can now build a fire kill 100% of everyone inside with monoxide, without damaging the valuables inside. They can't do that to a castle without at least storming the damn place first and taking losses while they do so. If you can defend your air vent meanwhile, why not just build on the surface?

Best realistic bet would be to take some giant existing cave chambers, and build structures inside of this. Otherwise the odds of digging out a suitable structure would be slim, you'd hits some damn fault or water seep and not be able to do anything about it.

Mining in hard rock won't follow a logical pattern suited to a city either, it will follow the ore being mined which is irregular. One exception to this could be a salt mine, because salt domes can be huge and very pure. Building into one of those would be ideal. But it would be very rare to find a salt dome in an upland or mountain setting. Not impossible for it to exist though.

Though then the problem becomes any uncontrolled water flow can actually seriously damage the city.

[Eternal_Freedom]

Didn't we have a thread a while back which was basically "build an SDN Bunker" in an old salt mine that could hold 1000+ people for multiple years? We even wound up with some pretty good drawings and diagrams of what stuff would look like IIRC.

[Zixinus]

Building something inside the mountainside is not quite the same as buliding it underground. It is harder.

[Elheru Aran]

Apart from ventilation, where do you put the sheer amount of spoil?

Natural caverns are one thing, but looking at Moria and the Lonely Mountain, they have significant amounts of excavation and sculpting of the living rock.

IIRC, in the final Hobbit movie, they show that some of the spoil from the Lonely Mountain's diggings had been piled up outside the entrance, so that was logical enough. If they're starting with natural formations and only refining them somewhat into a finished form, they might not even have that much in the way of spoil. But if they're doing significant digging and carving, well... they gotta put it somewhere.

I can see using it to fill cracks and to firm up foundations, that kind of thing. But that only goes so far especially when you start talking about chambers that are hundreds of feet tall and thousands wide/long, like the Dwarrowdelf in Moria. Real-world underground cities don't tend to go in for such massive spaces-- apart from the difficulty of holding up the ceiling, it's a LOT of work to excavate.

[Formless]

The point of such a city is also open to question unless its to protect against large monsters, since if the enemy merely seizes control of the air intakes on the surface they can now build a fire kill 100% of everyone inside with monoxide, without damaging the valuables inside. They can't do that to a castle without at least storming the damn place first and taking losses while they do so. If you can defend your air vent meanwhile, why not just build on the surface?

You're thinking about this as if the only defenses offered by an underground city was its fortifications like a castle. However, the defensive value of Cappadocia was that it was camouflaged within the geology-- if no one even knows where you are, how are they supposed to attack you? All they can see, if they can even find the right position to see it from, are a few buildings hewn from the mountainside; but its not obvious at first glance that its an entire city, and you certainly can't see all the tunnels that connect everything together. Its a place where people didn't just go to defend themselves, but to vanish entirely (kind of like how the Viet Cong's tunnel network protected them, only it wasn't meant to last as long). If you think about designing your city-under-a-mountain with disguise in mind rather than fortification as the principle defensive mechanism, then I think an underground city makes far more sense. Obviously, if it didn't work, Cappadocia and other sites like it would not have survived to the present day.

[Sea Skimmer]

No I'm just thinking about reality, and keeping anything you can call a city secret is contrary to the needs of a city. Do we mean a city, or some crazy cult compound where anyone who wants to leave is violently beaten back into the mine shafts?

A city needs trade to make sense, doubly so in fact if its underground where you can't grow food locally in any useful sense without electrical power. Also just about everything you want to do commercially involves making smoke,and that smoke has to vent out somewhere and fuel for its fire has to come from somewhere. You need a whole forest within a reasonable distance to harvest for that, the deforestation of which will be obvious for centuries. Also mountains by nature are barriers, and humans search along barriers.

Hiding a city's physical sight up a valley might work, in that you might control the land approaches enough to prevent any typical spy from sighting it, but at that point it wouldn't matter if it was underground or not. Vietcong tunnel systems weren't secret and existed for a far different and strategically offensive purpose, it's not comparable to the point need of a viable 1-10,000 person city to exist.

In fact I would contend that being hidden underground would only be a further strategic disadvantage, because the enemy will know you exist, know by nature you can be easily blockaded, and be mystified by what you might be hiding. Attracting attention in other words. Moria certainly seemed to be, but Moria did have that advantage of exits on opposed sides of a mountain. The problem is actually building straight through a mountain like that would be near impossible without explosives. Ways exist to try but say fire splitting rock 10 miles inside a mountain with the ventilation problem that creates is a nightmare. Let alone with people with limited understanding of engineering, and almost none of systems engineering.

[Broomstick]

Didn't we have a thread a while back which was basically "build an SDN Bunker" in an old salt mine that could hold 1000+ people for multiple years? We even wound up with some pretty good drawings and diagrams of what stuff would look like IIRC.

Yep, we had at least two of those. The notion was basically to build a comfortable human habitat within an old salt mine. Started with a RAR! involving Q and kept on rolling.

[Sea Skimmer]

We had a couple prior underground city threads too. They turn into a very very lot of elaborate digging.

I have one newish idea though, WHALING!

This will solve the blockade, heating and lighting problems all together. If this city was located near the seacoast on some kind of cape or large island that saw constant whale traffic. Whale oil was the cleanest form of lighting around before electricity, and lack of natural light is the crippling problem of being underground. Close naval blockades were not really practicable until the ships of the gunpowder era.

Meanwhile if you had a hot spring..fantasy but not magic, you could keep the place heated, though this might not solve your humidity problem, and humidity will be bad near the ocean. However you would not want the hot spring in the tunnels. You would want to to be piped in, because otherwise you'll probably have problems with outgassing from the water, like say the air turning into 20% radon.

[Crossroads Inc.]

Thanks everyone for the feedback! got a lot of good information in short time period!
Going off of what some have said... I think in terms of dealing with certain things, as well as "hiding in plain site" concept, of adding a a town near the entrance to the complex. Certain things that are hard to do, or indeed cause a lot of smoke, or are too dangerous, can be down in the town, which is just a normal town and can trade with others.

The reason of hidden, at least for my own purposes, isn't fear of invading armies, or barbarians. But pure secrecy and wishing to remain perhaps just a rumor.
The addition of a underground river can provide water.
I am curious if adding a "hot spring" might be dangerous, as hot springs are usually in areas of either volcanic activity or with other geological activity, and typically you would want a very Geological INACTIVE location for such a complex.
Also....

Building something inside the mountainside is not quite the same as buliding it underground. It is harder.

I am curious how having it up inside a mountain is harder than underground?
Is it a safety issue? Or simply of the difficulty in carving into solid rock?

[Zixinus]

The problem with building into a mountainside to hide things is that it essentially only works once. Once you know the path and/or have a map, that advantage is permanently gone. It would probably be enough to deter wondering threats like bandits or raiding nomads, but against an army and/or determined enemy, you are at best buying time.

I am curious how having it up inside a mountain is harder than underground?
Is it a safety issue? Or simply of the difficulty in carving into solid rock?

I'm basing this on a guess, but:

Because all the difficulties of building underground (creating support, creating vents and piping for water, excavating, etc.) are compounded by mountainous terrain. Lots of steep ledges, narrow roads, sheer rock, danger of winds and frost from weather, etc. It means massively complicating building external stuff like vents because of those things: it's not enough that you have to build something that's already very complicated to build, but you have to do it while digging into sheer rock, having to work on steep ledges all around, said wind and weather, etc.

Which can work to your advantage IF you can pull it off. You can do something like make essential air vents and water vents inaccessible from the outside by putting them in spots that are inaccessible (especially if you landscape it). Then it would require climbing wall-like mountainside. Of course the enemy can also landscape or still send skilled mountaineers to start fires in those areas, but it again creates a bottleneck. This of course depends on how those air vents and water pipes would work, which I have only rough ideas about.

[Broomstick]

An advantage to cave living is that the temperature tends to stay very stable underground. Now, this may not be a perfect temperature for people, as there are things like ice caves that are naturally quite chilly inside, as well as hot caves. There is also a trade-off between venting/fresh air and that temperature stability, but for very hot climates it seems to work well enough that we have examples of elaborate living accommodations in caves.

Dwellings embedded in cliffs, provided they have sufficient water supplies and food stores, can be very resistant to attack - various pueblos in the American south west seem to have served that function. You do have the issue of getting people and supplies up and/or down sheer cliffs during peacetime, but like I said, there are tradeoffs.

[madd0ct0r]

Didn't we have a thread a while back which was basically "build an SDN Bunker" in an old salt mine that could hold 1000+ people for multiple years? We even wound up with some pretty good drawings and diagrams of what stuff would look like IIRC.

We did, we also had a build moria thread using magic too..

[Zixinus]

Keep in mind that with caves, part of the reason they have stable temperature is because there is little to no air circulation. There is nothing to get the air hotter or colder. The moment you add people that breath in oxygen and breath out water vapor plus carbon dioxide plus other stuff , you have problems. You have to keep recycling air and heating the air (even in hot temperature zones, they get cold at night). You also have the problem of moisture, which can cause rot and decay in many kinds of building materials.

[Sea Skimmer]

Thanks everyone for the feedback! got a lot of good information in short time period!
Going off of what some have said... I think in terms of dealing with certain things, as well as "hiding in plain site" concept, of adding a a town near the entrance to the complex. Certain things that are hard to do, or indeed cause a lot of smoke, or are too dangerous, can be down in the town, which is just a normal town and can trade with others.

Having an underground annex would certainly be much more viable then a fully underground city. But remember before aircraft and balloons you can just hide stuff behind physical walls, and nobody can peek over if you control the entry strictly enough. So why build underground? If you have DRAGONS around this might make sense, but still you'd just need space for shelters. Keeping all your grain from rotting or the tunnels overrun with rats due to your inability to burn all your garbage because your stuck in a hole wouldn't be an issue if the place only got used for a few days or weeks at a time.

The reason of hidden, at least for my own purposes, isn't fear of invading armies, or barbarians. But pure secrecy and wishing to remain perhaps just a rumor.

But why and how? Also that idea would strongly favor adapting an existing cave system, because the labor requirement would be so much less to adapt it.

The addition of a underground river can provide water.

Be more useful as a sewer I reckon. You'd just have to be super careful people don't throw trash into that water (which they will) and block the drainage, causing your facility to flood. It would be good if that river was at a greater depth then your habitable space. You would absolutely not want it flowing right through the city.

Natural seeps will probably already provide far more drinking water then you need as is, the risk of an actual river is the flow might change and flood you out, and it keeps your air cold and humid. I think that goes back to 'favors cave' because at least with a natural cave you 'know' its basically stable long term. As opposed to digging into the ground...you hit water suddenly and can't stop it because you don't even have rock grouting technology..what to do?

Also it is an option to dig wells from a cave tunnel down.

The problem with digging though basically is without modern tech (and even then...) you are going to cut through multiple layers of rock strata. If you hit anywhere with water that water may not just drain into the tunnel, it may drain under high pressure and change the drainage pattern of a huge area and cause an unending problem. This isn't just possible but likely. This water also may be rather less then drinkable depending on local conditions.

I am curious if adding a "hot spring" might be dangerous, as hot springs are usually in areas of either volcanic activity or with other geological activity, and typically you would want a very Geological INACTIVE location for such a complex.
Also....

Hot springs can exist in areas that are functionally geologically inactive. But hot springs are not all caused the same way (other then in general terms). Some are warmed rainwater which has followed a layer of impermeable rock deep underground and then reemerged downslope. Others are the result of the normal water table being boiled by hot rock being forced upward, and I'm sure other scenarios are possible.

The heated rainwater method as is thought to cause the hot springs at Bath for example is pretty safe. If you were near serious volcanic or geothermal gyser activity though the water could be 1) so hot you die and 2) so full of minerals it's not just toxic, the minerals would buildup in your pipes and drainage channels constantly and block them. This is also where gasses in the water become very likely.

Also for bonus if you dig the wrong spot your tunnel will try to fill with methane.

The problem with building into a mountainside to hide things is that it essentially only works once. Once you know the path and/or have a map, that advantage is permanently gone. It would probably be enough to deter wondering threats like bandits or raiding nomads, but against an army and/or determined enemy, you are at best buying time.

How is that different from building anywhere else to hide things? I mean I'm not a fan of hiding at all, but I don't see how this is relevant to a mountain? A mountain range at least blocks an enemy from one or two directions (see the Swiss). It might also provide an economic rational for the city to exist if it controls a fortified mountain pass.

You go build underground out in the more open lowlands and your creating a host of new problems. Water runs downhill, silt runs downhill, and lots of humans will already be presnt. You aren't likely to find a good spot in the lowlands. The mountain you use doesn't have to be 16,000 feet either BTW. A lot of mountains in the world are fairly low, but can still be steep enough to be useful defensively. The taller the mountain the more water will be inside of it.

A 3,000ft mountain with steep sides and narrow width would be the kind of spot your looking for, the water problem is proportional to the size of the catchment area 'above' the tunnels, so the less mountain above you the less water out of hand.

Because all the difficulties of building underground (creating support, creating vents and piping for water, excavating, etc.) are compounded by mountainous terrain. Lots of steep ledges, narrow roads, sheer rock, danger of winds and frost from weather, etc.

Those issues are entirely dependent on the exact building site, hard rock cut tunnels for example need no supports unless the ground is badly faulted (probably a deal killer in this context), while limestone or chalk would but are far easier to tunnel into, but so easy in fact that an enemy could begin sinking his own tunnels to invade with. Chalk is good at blocking water, limestone is rather not, but also much more likely to be well drained (as opposed to a standing water table). Meanwhile you go build underground out on the plains or in foothills and your odds of being flooded out in an era without cement or electric pumps is going to start to get bad. And you certainly won't stay secret.

It means massively complicating building external stuff like vents because of those things: it's not enough that you have to build something that's already very complicated to build, but you have to do it while digging into sheer rock, having to work on steep ledges all around, said wind and weather, etc.

Yeah won't be easy. In fact it might consume centuries. But there is no point in building anything if it can't be made habitable, and that's where digging directly into the side of a mountain at a slight up slope has a big advantage over anywhere else. You can then 100% rely on natural drainage. Everyone won't DIE OUTRIGHT from an unexpected rain or water seep causing flooding (remember no flashlights, any emergency is realllly bad, accidental fires too).

Mountain slopes always have wind too, so you can make wind traps that might provide some of your draft without external power. That's pretty damn important if you don't even have steam power. Early deep mines used furnace draft, literally they built a fire to move the air, and that method absolutely sucks. But it works better and better the taller your chimney for draft.

ind traps would need to be huge, but they could probably work if they were huge enough. That's better then some options! Medieval water wheels BTW provide extremely low power levels, you wouldn't get far using them for vent fans.

Building your air vents into fortified towers on mountain slopes is basically the only place you could put them that they would not be excessively vulnerable. If the site is not geographically isolated then its defensive advantage is no greater then its weakest point. Which means you then need elaborate and heavily manned surface fortifications, and have defeated the point of shoving everyone in a hole. Sure its a pain in the ass to build, but so is this entire idea.

[Kingmaker]

Your archetypal subterranean city in fantasy is built by dwarves - who (usually) live hundreds of years, are extraordinarily patient, have more sophisticated science and technology than everyone else (often thanks to a helping hand from the local god of engineering), and (most importantly) seem to have an active preference for living underground/inside mountains. Dwarven architects might be considerably more blase about a project taking hundreds of years than their human counterparts. The economic rational for the cities is usually that they're on top of some stupidly massive ore deposits that dwarves found... somehow.

I've seen the food issue addressed a variety of ways. One of the more amusing ways I've seen it explained was rationalizing the stereotypical dwarf's alcoholism: beer is the actual staple food, which addresses the long-term storage problem, I suppose. I assume an actual human attempting to survive on a diet primarily of dark beer would die, but dwarves are fantasy creatures with magic physiology. *handwave*

Logistical issues like ventilation. drainage, and spoil are usually ignored outright or handwaved away (e.g. the ventilation shafts are all said to be in super-inaccessible parts of the mountain).

[Lord Revan]

Tbh beer and other alcoholic drinks are a good way to store drinking water in days before modern hygenic practicies and frigidration, also alcohol can be used to as a preservitive, so even if the dwarves ate/drank other things then beer it would probably make up a considerble portion of their diet.

[Elheru Aran]

Magic Dwarven physiology could explain a few other things as well. Their durability (evolving to deal with heavy digging, occasional rock-falls, etc=stronger musculature to height, stronger bones, etc), being able to subsist on less oxygen and more CO2/CO/etc in their atmosphere, being psychologically inclined to deal better with underground living, evolving an ability to extract the necessary vitamins and such from whatever food they keep stored underground... and so forth.

[Sea Skimmer]

I've seen the food issue addressed a variety of ways. One of the more amusing ways I've seen it explained was rationalizing the stereotypical dwarf's alcoholism: beer is the actual staple food, which addresses the long-term storage problem, I suppose. I assume an actual human attempting to survive on a diet primarily of dark beer would die, but dwarves are fantasy creatures with magic physiology. *handwave*

Most beer in real life only keeps for about six months, and brewing consumes very large amounts of wood burning energy, a lot more then baking bread or making hardtac. Doesn't solve anything, it makes the problem worse in certain respects. The Dwarves would need to be able to survive on IPAs...

Logistical issues like ventilation. drainage, and spoil are usually ignored outright or handwaved away (e.g. the ventilation shafts are all said to be in super-inaccessible parts of the mountain).

The best is when the Dwarves also have a damn coal mine as part of their actual city as the energy solution. Because nothing could be a better idea then burning a shitload of coal beside a coal mine, inside a tunnel!

[Zixinus]

How is that different from building anywhere else to hide things? I mean I'm not a fan of hiding at all, but I don't see how this is relevant to a mountain? A mountain range at least blocks an enemy from one or two directions (see the Swiss).

I'm just criticizing the advantage of concealment of a mountain fortress from the investment standpoint. It is not a bad advantage, but only really works if the enemy is not actively looking for the place.

Controlling approaches to the fortress by taking advantage of mountain terrain is different thing, one which I agree with.

Tbh beer and other alcoholic drinks are a good way to store drinking water in days before modern hygenic practicies and frigidration, also alcohol can be used to as a preservitive, so even if the dwarves ate/drank other things then beer it would probably make up a considerble portion of their diet.

Yes, but that's true of any civilization that has alcohol and doesn't have readily available potable water on tap.

Those issues are entirely dependent on the exact building site, hard rock cut tunnels for example need no supports unless the ground is badly faulted (probably a deal killer in this context), while limestone or chalk would but are far easier to tunnel into, but so easy in fact that an enemy could begin sinking his own tunnels to invade with.

Yeah, the viability really depends on the geology of the place as much as the geography.

Yeah won't be easy. In fact it might consume centuries. But there is no point in building anything if it can't be made habitable, and that's where digging directly into the side of a mountain at a slight up slope has a big advantage over anywhere else. You can then 100% rely on natural drainage.

I was actually trying to talk in a different context, that of the problems while building the mountainside fortress to begin with.

[Gaidin]

Hilarious question this thread has yet to answer. Are we founding this hilariously mined out city for economic or military reasons?

Because...your utterly hilarious metaphor to Moria had an utterly priceless mineral to mine. I'm just saying. It might have been a worthwhile economic investment.

[Broomstick]

....just don't dig too deep....