Worldbuilding Stack Exchange is a question and answer site for writers/artists using science, geography and culture to construct imaginary worlds and settings. It only takes a minute to sign up.
Sign up to join this community
Cities usually emerge at places where transportation is easy (on a plain, near a sea or a river, etc.) so that people can come and go (facilitating trade) and water and food can be brought to the city.
Under what conditions can a big city emerge on a mountain (for example in a valley)? How large can it become in the middle ages? What about the colonial or the industrial era?
The choice to build a city atop a mountain is governed by the balance of defense, resources and proximity. With a nod to tradition.
(Note: my answer is addresses an entire "city ON A mountain." Not "located near a mountain," "located within a mountain range," nor "nestled between mountains;" not a "castle on a mountain" with a city nearby below; not a city "on a relatively large hill." However, in any of these cases, all of the conditions below still apply, including the excellent answers and comments of the other esteemed contributors.)
Having an entire city situated upon a mountain, plateau, or mountainous hill is unusual enough to merit an analysis of its attributes.
Defense: Remote proximity from potential enemies, greater field of vision for surveillance, height advantage in combat. Safeguarding the nearby trade routes (roads and waterways) by being close enough to oversee them and to quickly deploy troops when necessary. Proximity to natural barriers that prevent enemy entry (rivers, seas, mountain ridges/cliffs, canyons) and to the structures that allow trade access despite these barriers (bridges, harbors, mountain passes, switchbacks). The nearby natural barriers protect the city, while the city protects the nearby trade structures.
Resources: Starting with food and water. A small town may hunt and farm the surrounding foothills, but it is difficult. Therefore in any larger settlement trade with nearby communities is also essential, and a proximity with them is also imperative. Cities built within mountain ranges are often in a valley bowl that is arable.
One acre of crops can feed up to 20 people for a year, if it is managed extremely well. See: https://www.quora.com/How-many-people-can-be-fed-year-round-off-of-one-acre-of-crop-growing
In colder climates the water can be collected from wells fed by snowpack runoff and natural aquifers in the mountain, but in Mediterranean or desert climates (near sea level elevations) the wells would have to extend down to the water table (sea level) just to fill a bucket. In these arid climates the majority of water was delivered by porters who trekked daily to retrieve it. This again requires a practical proximity. As a secondary system Masada had cisterns to collect rain. A mechanical water delivery system is plausible, but they tend not to work in the real pre-modern world. It is far more likely to have discovered volcanic activity producing constant hot springs near the top of a mountain.
Mining resources are a strong possibility, but not feasible without trade established among other cities, which again requires either proximity or waterway transportation. In this case it is more likely that the town sprung up around the mine, to house the families of miners, and businesses to cater to the families.
Religious Directive: (@AarthewIII - ingenious!) The deity/prophet indicated that this his desired location, holy ground, the birthplace of the deity/prophet, the burial grounds of ancestors, the place to make a stand against the encroaching enemies of the faith. Or simply tradition. (Some would argue that the deity aims to protect his flock, via all the wisdom given above.) The deal is: if the location of the city is not defensible and sustainable, then the next generation does not survive to carry on the tradition/religion.
To ensure we are defining like attributes here is a quick chart with notable "mountain cities," as defined in the chart:
And because some cities on large hills are very interesting, here is a chart of "hill cities," as defined below:
(Any good suggestions made in the comments below will be considered for the next update.)
It's all about reasons. You need a reason to build there.
There are two reason that lots of inaccessible areas got settled in our world.
Defense. The city's position makes it very hard to attack. In a hostile area this defense may be more important than accessibility.
Resources. There are rare and extremely valuable resources here, for example gold or diamond mines.
Either of those things might make it valuable enough to be worth importing the food etc.
The size limitation is hard to answer because it depends on just how much the location is worth. If there is enough reason for enough people to be there then surprisingly large. Certainly thousands of people.
Consider a very important factor: safety. I'm not into Game of Thrones, but I have some fading memory about a castle on a mountain that is so incredibly hard even to approach that it's practically impossible to conquer.
Also, logistical hubs - /r/worldbuilding provided this amazing chart:
The right side may provide help for you. I can also see the point in a city used to rest in a tough mountain ride.
Actually, these two, as you can see, are quite important aspects of settlements, and even though they are not the only options, they are noticeable in several cases. Even when I was as young as 11, I was taught in history class that in Europe, several former Roman settlements were used in establishing new cities - and needless to say, they were the very professionals at both.
Let us first look at reasons to build cities/castles in general.
*This is different from 1) because the city is not built because it protects itself but because it protects the nation.
Ok, so the only reasons that would work for a mountain city are 1-4. (Mountain farming is hard, just look up steppe farming. No fun, the Mongols got bored of it and decided to invade China and Europe.)
As far as part two "how large can it become …" really depends on how much the nation or its people want to live there and geographical location. You could consider a valley city right next to them that they get food from. This would boost their population. The size and fertility of the mountain and valley will effect its population as well.
Many Italian towns and cities are on the top of hills. Rome is famously built on seven hills. The reason is very simple - it makes your town/city easier to defend. If you're living in a nice civilised society, this isn't an issue. But if you're in a society consisting of a loose coalition of petty princedoms, any of whom might decide to have a skirmish with their neighbours over a matter of honour or simply because the aristocrats at the top think there might be some benefit to themselves, then you have a strong reason for strong walls.
Greece also has a lot of towns and cities on hillsides. This is a slightly different reason though - there simply isn't much flat land to build on, or to farm. Most Greek towns are on the coast because the sea was the only reliable way to get enough food, and most Greek coastline goes straight from shore to mountain with very little flat space in between. So you see a lot of towns built on the side of hills, on the least-worst slope of course, but still with substantial amounts of up-and-down.
A mountain was hit by a meteorite, leaving a huge crater that filled with water, forming a freshwater lake capable of supplying a city built on the part of the mountain that was not destroyed by the meteorite.
The lake was afterward stocked with fish, and overflow from the lake is directed via irrigation ditches to terraces built against the mountainside.
To repel invaders, extra water is held behind a dam, to be released down the only road leading up the mountain.
Mining operations are facilitated by water power, and sluice-works for separating ore from rock.
To allow the nobility to escape rapidly in case of disaster, a gondola runs to a well-defended neighboring peak having a lower elevation. The cables for the gondola are made from woven bamboo, which the Chinese discovered over a thousand years ago is nearly as strong as a modern steel cable.
The society has nobles, each of whom is the "lord of all he surveys". In order to maximize the territory he rules, each noble establishes his capital at the top of the local mountain with the best views.
In ancient and medieval times, these cities will have populations of a few hundred -- servants, guards, clerks, porters, smiths, armorers, bakers, barmaids, et cetera.
The mountain-top cities use line-of-sight communication methods. Early on, these might be smoke-signals, heliographs, and/or semaphores.
These cities will benefit from developing windmill and pumping technologies early. Windmills can power deep wells, to provide water for "hanging" gardens and/or hydroponic farming. Windmills are also similar to some semaphore signalling technologies. If iron ore, copper, and silk are available, the blacksmiths might develop electric motors and electric generators relatively early.
Colonial America had printing presses, windmills, smithies, and tiny colleges.
By 1834, Vermonters could afford silk wedding dresses. Blacksmiths could visit Institutes with experimental electromagnets. This allowed them to invent electric motors, electrified railroads, and electrified printing presses. If they had reversed the motors, they could have had generators too.
With the hypothetical culture's focus on line-of-sight long-distance communications, inventors might skip over telegraphy directly to radio. They might move on to microwaves and/or lasers. Communications and electronics research facilities could grow up in these cities. Eventually, television stations, computer manufacturers, and aerospace firms might be found in these cities.
Try google "kogi mama" and/or Alan Ereira, watch his video (aired by BBC in 1990) and be amazed. These stone age people who still live in Colombia built sustainable cities on mountains for over a thousand years, housing more than 25.000 inhabitants. Very impressive! In the film the requirements to build such a city are also summed up..
Depending on your world, if you have easy access to flight, especially VTOL, then building on a mountain is just as much sense as building along a river delta.
