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I am taking inspiration from games like Dark Souls (Dark Souls 1: Lost Izalith, Dark Souls 2: Shulva - Sanctum City, Dark Souls 3: Profaned Capital) and Elden Ring (Eternal Cities - yes it is underground and the ceiling is illuminated by light-bugs), where the player can sometimes make his way to entire cities that are buried underground or are found inside giant caves that have seemingly formed around the city. Weirdly enough, the city layout, roads and buildings are sometimes left intact. Additionally, on top of the city, in the surface, the people are either completely oblivious to its existence or consider it to be ancient ruins or a long lost city of some legend.

What are ways that cities can end up buried deep underground (~100 or more meters in depth) but remain intact and retain their general layout?
Could this be possible in real life?

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  • $\begingroup$ does the city need to be navigable or can it be completely filled. $\endgroup$
    – John
    Apr 12 at 21:36
  • $\begingroup$ @John I has to be accessible to some degree, at least a part of it. $\endgroup$
    – Lae
    Apr 13 at 4:02

3 Answers 3

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Have you heard of Pompeii?

Pompeii was covered by volcanic ashes. It was covered so well in the ash, that not only the town was left almost completely intact, but also people were covered by it and preserved in the situations they died in!

All it took to reveal the place again were shovels... but in your word, the place could be covered in ash first, then a hard volcanic rock forming above, then water ingress washes the ash away again, and voila! A mostly intact place in a cavern!

As alternatives to volcanic ashes, which are almost insoluble in water, salts could be deposited by constant wind within a few days, covering up the town fully. Salts would more easily wash away and leave the town in a cavern.

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    $\begingroup$ I was going to come in and write this answer $\endgroup$
    – Esther
    Apr 11 at 19:21
  • $\begingroup$ This is very interesting. I makes me think of other structures buried in the desert or some similar place... Could this be pushed even further? To the point where the city is buried deep underground, like 200 meters or something? $\endgroup$
    – Lae
    Apr 11 at 19:22
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    $\begingroup$ @Lae It can, depending on the happenstances: The 35 meter ash cover is the preserving layer, but what actually puts the pace underground are the subsequent layers of lava and other rock depositing above. There only needs to remain a way for water to ingress and wash away the ash. Other deposits might also work, such as a very harsh storm depositing tons of salt in the place, which washes away faster. $\endgroup$
    – Trish
    Apr 11 at 19:37
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    $\begingroup$ @Lae No, the kind of volcano that can bury a city without destroying it will not bury it more than a few meters over the timescale of human civilization. $\endgroup$
    – Nosajimiki
    Apr 13 at 2:28
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It was built this way

Throughout the world, there are a number of cities that were built entirely underground. Some are very ancient like Derinkuyu (up to 85m deep), but some like Wieliczka (up to 327m deep) are relatively modern. When a city starts off underground it only takes a simple cave in to completely cut off the city from the world above. More importantly, they can end up over 100m under ground in non-geological time-spans... 100m of natural sediment is very unlikely to exist anywhere over the course of the brief amount of time that people have been building cities.

So if one of these cities were to be cut off by an earthquake or something of the sort, you could later dig into it, and not just have a well preserved city, but it could be practically move-in ready like your examples.

enter image description here

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  • $\begingroup$ The links you provided are very interesting. The first reminded me of catacombs. $\endgroup$
    – Lae
    Apr 12 at 0:39
  • $\begingroup$ Volcanic activity can result in a few hundred meters within a manner of just a dozen years. $\endgroup$
    – Trish
    Apr 12 at 8:27
  • $\begingroup$ @Trish In order to bury a city in tact, it has to be a Pelean type eruption to give the lava time to cool into ash mid-air before settling over the landscape. While a much more effusive Hawaiian type volcano can build up the landscape quite a bit over the course of decades of constant lava flows, such a volcano would completely melt/burn away any evidence of a city ever existing. Pompii was only buried about 6-7 meters after 1700 years and 3 dozen subsequent eruptions from Mt. Vesuvius. $\endgroup$
    – Nosajimiki
    Apr 13 at 2:24
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The new city was built on top of it

Many cities, particularly older ones, tend to have a vast underground network of unused tunnels beneath them. Think Old New York underneath New New York in Futurama. London and Paris are two notable real-world examples of cities with a surprising amount of abandoned sewers and subway tunnels beneath them, and in some cases secret groups of people who still use them for various purposes. (In Paris a number of years ago, a state-of-the-art theater complete with bootlegged copies of not-yet-released films was discovered in the sewers, which promptly disappeared before the police could investigate further - they still don't know who was behind that.) In some places you can pay to get a tour of the secret underground areas.

If you fast forward this trend a few hundred years, it's not unreasonable to imagine this industry growing into a full-on subterranean city beneath the city proper. If you don't want to have your city underneath another city, you could write an apocalyptic event that destroys the surface city, and leaves the underground relatively unscathed (or even forces some of the surface-dwellers to retreat into the underground.)

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  • $\begingroup$ A good fictional example of this is Ankh-Morpork, which is built on top of older cities. $\endgroup$
    – Burgi
    Apr 13 at 13:36
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    $\begingroup$ @Burgi Ankh-Morpork is of course a pastiche of several real-world cities, including London, so it shares that characteristic. $\endgroup$ Apr 13 at 13:45

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