Would a medieval Arcology be possible?

Question

In a barren desert, 5 cities called the desert pearls are placed like pearls on a string.

Travel between the cities are done with huge pack animals who looks like a breed between elephant (mammoth) and rhino with thick brown fur (maybe like wow clefthoof?), able to walk without water for weeks. The size of the creatures also makes them slow and vulnerable to attacks.

Caravans are transporting everything, silk, food, hides etc. The desert is dividing a continent, the same way the Atlantic ocean divides America and Europe.

The desert is dangerous and unforgiving, wildlife is desperate and dangerous, scorpions the size of a small car, desert wolves hunting in packs, and other creatures no one lived to tell the story about.

This caused the cities to wall them selves, with no production from outside the walls, the cities are vastly depended on the caravans traveling through.

My main concern is that food production in desert areas are limited, and hunting is close to impossible outside the walls (Unless the hunters are brave or stupid). The area you need to farm for the amount of people vs. Area of the walled cities, beside it is difficult to increase the area inside the wall. It would require expansion of the walls, more guards to patrol and so on.

But would it be possible for such cities to be self sustaining in the time between caravans (Maybe permanent). Lets say in case 3-4 caravans never arrived. (Time between caravans are 2-4 weeks, sometimes more special deliveries (rarely brings food and water), sometimes less since caravans never arrives.)

How would the cities be designed? Take into consideration creature size, food production, diseases, habitat, population growth etc.

Answer 1

The main problem will be water.

When you want to sustain a larger population, you need large-scale farming or fishing nearby. Especially when hunting and gathering is ruled out by the dangerous wildlife. Also, the population will require water for drinking.

That means each city needs some kind of water source.

An oasis or river would be the logical option. On earth, cities in desert regions always formed near these.

When you want to be more exotic, you could also have an underground lake or river in a cave system below the city. When the cave system is large enough, it might be an option to move the whole city into the cave system. That would offer protection from the wildlife, sandstorms, heat and invaders. The underground water source might also allow fishing. They could trade the fish for other food with the caravans to get a more diverse diet.

You could also go for the "a wizard did it" solution and solve the problem using magic. A caste of wizards or alchemists could know a secret how to create water. This would put them in a very powerful position.

When you are determined to do without any open water source, you could invent a special kind of crop which requires almost no ground-water to grow, but still creates very juicy fruits by absorbing moisture from the atmosphere. These could be a source of both nutrition and fluid.

In Frank Herbert's Dune universe, desert settlements get their water by extracting moisture from the air by technological means. They also preserve water by wearing special suits which absorb and recycle all fluid their bodies lose, so the drinking water consumption is reduced to a minimum. But considering that you tagged this question as "fantasy-based" you are likely not searching for a high-tech solution.

Farming

No matter which route you choose to solve the water problem, the city will need some area for farming. You could expect most buildings to have flat roofs with gardens on top. But that would still be unlikely to be enough to satisfy the hunger of the whole city. You will need dedicated farmland (although I am unsure how much you need - I created a new question for this). An option would be to have them outside the main fortification of the city, but behind an outer, less strong and less guarded fortification. This would keep out all but the largest wildlife creatures, which could then be fought in an organized manner from the main fortification. The secondary fortification could also be partially substituted with a natural barrier like a cliff, chasm, mountain range, water (when you allow it) or something more fantastic.

Answer 2

Storage

Missing caravans aren't a problem if the city is taking precautions against such fluctuations and storing grain. Which they obviously are - pretty much every ancient city (in Babylon, Egypt, etc) was fed by grain and had to store a supply of at least a full year of grain simply to last until the next harvest, and often stored much more. Grain could reasonably be stored for at least three years. See also the biblical story of Joseph as an example that probably is a bit exaggerated, but still close to reality.

The requirement to store food doesn't change anything at all - no matter if your city is in the middle of desert or in the middle of the most fertile land in the world, anyway it would be importing and storing the grain within itself. The only difference would be in the distance of transportation and thus the price of food.

Answer 3

If I were to design a desert arcology, I wouldn't rely on the construction of walls around a city for my defense. Instead, I would rely on the geological structures of my environment to protect me from my enemies. Deep canyons and tall mesas would both offer me formidable defenses in most directions. I could fortify the few entry points into the region and convert the interior into farms.

For canyons, I would base my city around the ancient city of Petra. All entry into the city of Petra must flow through a narrow passage, called the Siq.

This canyon could easily be defended from marauding beasts or bandits. The canyon opens up into a wider valley, the floor of which could be farmed to feed the city dwellers. In Petra, the city dwellers then have another layer of defense, in that the city is carved into the canyon wall. If creatures managed to breach the outer perimeter, all of the inhabitants could lock themselves inside while guards cleared the fields of monsters and re-established the perimeter.

Likewise, imagine if your city was built on top of this:

Desert animals would be blocked from getting to most of the city by the cliffs surrounding it on all sides. Any lower angle portions of the cliffs could be fortified and used as entry/exit points to the city. The downside of living on a mesa would be that there would be less water to grow food with, but if there was a reasonably high aquifer or an underground river flowing below, deep wells could be drilled down through the mesa through which wind powered pumps could pull enough water to irrigate the farms.

Answer 4

If there isn't a lot of water, you will not have a city. You will have a fortified caravanserai with wells inside the walls, mostly empty space for the travelers with the necessary number of guards and a director. They may use the roofs to grow feed for the animals.

You will need these spaced about one day's travel apart.

The animals you describe are implausible for deserts. Desert animals are lean and lanky to lose excess heat easily, with enough hair to stave off sunburn but not so much as to make them hot. Consider the difference between the Arctic fox and the desert fox, or between the Bactrian (cold weather) and dromedary (hot desert) camel. Also, anything very gigantic is going to find it impossible to traverse ergs (sand dune areas): it will sink right in when it tries to climb. It would be restricted to rocky desert areas.

Look at the oasis cities of the Garamantes as your models: they were a culture in the middle of the Sahara. But each one needed the springs of an oasis to exist.

Large predators are normally very rare in desert conditions. There isn't enough large prey to support them. "Desert wolves" are normally semi-desert wolves that live on antelope and wild asses that live on the scrub. They would have no reason to risk their lives going into the true desert unless they got the timetable on when caravans were coming through and knew they could probably score a meal. If they normally go after migrating herds, you have an excuse for them being there.

Now, about city layout. Most people have a funny idea that a medieval walled city is like a neolithic walled village: houses packed cheek to jowl and the tiniest possible wall around it. Not so. The problem is that most people are thinking of the 19th C remains of 12th C cities. Land was so valuable that everything was overbuilt. Back in the day, city walls were built as large as possible, and buildings clustered along the streets leading from the gates to the city center. Back from there, houses had gardens, and there was wasteland along the walls for riding academies, dairy farms, and stonecutters. There were orchards inside cities.

Under these circumstances, there will have to be enough land allotted per person to support them with a garden (yes, rich people buy land and get bigger, but maybe allocation isn't capitalistic)(in which case, rich people pay the poor ones to do the weeding). Meat sources are likely to be birds with clipped wings (chickens, pigeons), small mammals (guinea pigs, rabbits), and omnivores that can eat the trash (pigs). Pigs may be branded then let loose to be the street cleaners. This was normal in Colonial America. People may brand their date palms.

Simply, you have to make living here a paying proposition for the inhabitants, or they will move somewhere else. Plausibly, they don't stay somewhere because an author tells them to. You have to give them a means to scrabble through and a reason to put up with the hardship.

Answer 5

They could capture migrating birds, grasshoppers or larger beasts for food.

It's not unusual for birds to use cities as stop-overs on a migratory route. The cities create thermal updrafts and may be associated with food sources. On Earth, many birds traverse desert and both zebra and wildebeest migrate through deserts to some extent.

I understand capture of large animals out in the open is not an option in your scenario. However, it would make sense for a city to be located near a mountain pass which all travellers must pass through, if only to collect a road toll. If the pass is also used by migrating animals and you're in the business of building walls, you can funnel herds of animals into enclosures, ready for consumption.

I realize this does not describe a proper arcology, but at least provides an intermittent supply of food. You can imagine that the cities have a degree of self-sufficiency like you describe, but during a prolonged crisis in the city, you'll also have the option of introducing migrant animals as a surprise solution, rather than having to stretch the credibility of their self-sufficiency.

Answer 6

If these places exist simply to provide a location for the caravans to recover, they will just be tiny outposts rather than cities. In order for these to be cities, they would need to be largely self-sufficient, as well as have some reason for existing. A person eats a lot of food in a month, but thousands of people eat truly enormous quantities. People in the desert also need significant amounts of water per day - hot dry climates take it out of you faster than you think. This is implausible to supply via mammoth camels. Food for a handful of outpost guards I could believe, but more than that becomes problematic (the more people need to be supplied, the lower the capacity for actual trade goods, and the higher the overhead cost - each pack animal will need more fodder as well, meaning additional carried food or farmland).

What kind of desert are we talking about? Is this endless giant shifting sand dunes like the Sahara or semi-desert hard scrub like the Kalahari? Regardless of the geology, you will need to think about the ecology of the desert. How do these dangerous animals roaming the desert get enough food and water to survive when there isn't a handy desert mammoth wandering by? Whatever water source you use is going to be an incredible draw for local wildlife (and was before the city developed), as are any crops being grown.

These locations are going to need generous sources of fresh water as well as some good soil for growing food for the city (both to feed the people and fodder for the animals unless they can make the entire trip without eating, which seems iffy). This could either be a cluster of waterholes developing a biome for a large area of arable land, a floodplain on a river (could be only temporarily above ground), or go with something a little more exotic like using some deep-rooted trees to grow food and provide water (tapping trees for water being a very intensive use). The less rich the soil and less plentiful the water, the more farmland will be needed per person for food - the exotic trees example would require massive amounts of territory to support a city, so probably only in a 'safe' area of the desert without many dangerous animals (or at least safe enough a small contingent of camel cavalry could protect roving bands of harvesters outside the city walls).

How is the city constructed? What materials are they built out of? Clay/mud bricks or stone? Almost certainly locally sourced as shipping building materials would be ruinously expensive. How the cities are built will be entirely dependent upon their location - perhaps scattered watering holes supporting some farming plots (or dug wells with smalelr gardens) would be surrounded by a large ring of houses (farming in the protected courtyard within the communal walls of adjoining buildings) as the city itself ending up with a streetless honeycomb plan like Çatalhöyük where the outer walls of the houses were effectively the city walls (no need to expand some arbitrary city walls, use the roofs as streets, and no real worries about animals who don't climb ladders). Expansion is as simple as building one new house at a time - eventually you will close off a new safe area in which to dig another well and have more gardens (so long as the water is plentiful).

Sanitation will be a major concern, and all resources will be precious - feces will certainly be needed as fertilizer (urine for ammonia too), so illness is a serious issue. Foods would be beer and thoroughly boiled gruel (killing bacteria in tainted water and fecal contaminated veggies).

Basically just think of the geology (the soil/sand/rocks and the river/oasis/wells) which informs the ecology (how do the wild animals survive) as well as the construction of the cities (on a riverside or lake, on top of wells, surrounding a spring, etc).

Walls will depend on what threats they face - thick or thin (small animals or herds of wild mammoths desperate to batter their way through?), unmanned or heavily patrolled (dumb non-climbing animals or climbers who don't slow down at vertical surfaces - solitary animals or in swarms?).

Transport across seemingly endless and very dangerous desert is expensive, so what is worth the effort of doing it? Why do so many people live there when it is so hard to survive?

The possibilities are endless, so break it down to the most basic level and build up logically with an eye to ecology and economics.