I have been wondering what would be more practical in a post apocalyptic setting, trying to restore the ruins of old (like refurbishing what can be restored and rebuilding over what cannot be and making the ruined cities livable again by degrees) or tear everything down, essentially turning the ruins into mines, recycle the materials and build anew in other locations?

For additional information the civilization that would be doing the rebuilding would have a level of technology comparable with mid 21st century humanity, so close to the present day but a bit more advanced. And for the cataclysm I was thinking something akin to a technological collapse, creating a domino effect that would lead the whole previous civilization to come undone completely and utterly with it, lowering considerably the planet's habitability and crippling the biosphere but not to the point of making it forever uninhabitable, just a lot more hostile.

What would be more feasible? Rebuilding/Refurbishing or tearing down as much as possible and recycling?

As for how old the ruins...let's place them at about 100 to 500 years following the collapse, the time needed for the planet to recover with some help the needed habitability to live on it's surface without protections.

As for the technological level of the civilization that build them, let's suppose a mid 22nd to early 23rd century, they were pretty much a type 1 civilization.

Among their technologies there were: advanced nanotechnology (capable of limited self-repair), advanced materials (which made their arcologies possible), robotics and AI (supported by advanced networking and computing apparatuses).

They also employed technologies to control the dynamics of their world (such as weather patterns, pollution and other aspects of the atmosphere, hydrosphere and even lithosphere), which is how the the technological collapse led also to the collapse of the planet's habitability.

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    $\begingroup$ There is "no one size fits all" answer. If the deterioration is light, it's better to restore. If the deterioration is significant, it's better to rebuild. $\endgroup$
    – Alexander
    Sep 10, 2021 at 21:02
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    $\begingroup$ How long ago was the collapse? If it's been more than a few decades, well, modern environments require constant maintenance and refurbishment. Plastics denature and crumble, paint flakes away, exposing the material underneath to environmental damage, road surfaces crumble because of freeze/thaw cycles, roofing fails after 20-30 years which lets water into buildings, storm and quake damage go unrepaired, etc. After a few decades, there won't be much worth restoring. $\endgroup$ Sep 10, 2021 at 21:11
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    $\begingroup$ @JuimyTheHyena that's a big range many things will survive 100 years very little will survive 500 $\endgroup$
    – John
    Sep 10, 2021 at 21:54
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    $\begingroup$ It was okay until nanothech part - it was 500y nothing to scawenge and nothing to restore, 100 eeeh maybe reusing restoring. But with nanothech and self repair it totaly a different can of worms - it depends - but main problem will be do they have sufficient knowledge to anything scawenging and reusing. It looks like with all that you have hadwave tune all the components -any combination is legit - u set the proportions and thus it defines what's possible. And then you may ask us if it looks okay. Best case obiviously reuse restore if they have knowledge and if they can. $\endgroup$
    – MolbOrg
    Sep 10, 2021 at 22:17
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    $\begingroup$ @JuimyTheHyena probably the opposite, technology is rarely made to last these days. older tech lasts so long because it was often overbuilt because there was no way to really model tolerances that well. Or because they used natural material like stone. plus planned obsolescence is a thing. $\endgroup$
    – John
    Sep 10, 2021 at 22:31

4 Answers 4


It is also interesting to ask if any technology from 100-500 years ago is in use (or at least functioning) today, and the answer is... yes. Now admittedly they are likely to have had some maintenance in that time, but it still gives us some useful reference.

This list is made from my own recollections of old things and spending 30mins on google. Contributions welcome!

Starting at the close end:

  • 1931: Empire State Building 102-story, quite a historical building
  • 1930: DC3 airliner. Not quite 100 years yet, but some still airworthy and flying
  • 1927: Model T ford. again not quite 100 years since it's production run. There are still some of these still operated by enthusiasts
  • 1914-1918: Anything from World War 1. I'm quite sure there are still operational pistols, lanterns, armored cars etc.
  • 1914: Panama Canal Locks
  • 1911: Hydro Power station in Akaroa, New Zealand. Not currently tied to the grid, but the pelton wheel is still spinning the alternator. There are probably other hydroelectric systems from this era. I've personally spun the remains of another pelton wheel from the same era that had sat outside unmantained for ??? 50? Years. The bushings on those things last forever and apparently had enough grease on them that it hadn't seized yet.
  • 1909: Bleriot X1 aircraft. Yes the original is still flying! Yes of course it has seen refurbishment in that time.
  • 1909: Peter the Great Bridge funny, 334m long bridge across the Neva River in Saint Petersburg, Russia. Most of the construction is original, besides paint job and that middle thing which opens.
  • 1897: The Wa165 steam locomotive, which still does tourist runs in Gisborn, NZ. I am sure there are plenty of other steam locos from this time that still operate.
  • 1858: Suez Canal. Dug by man, still used.
  • 1844: Oldest remaining house in Canterbury NZ. Still lived in today by the family (surprisingly, I have bumped into one of the current generation!). I am sure Europe has far older houses/halls.
  • 1840: Lichenstein Castle. Currently lived in by ... the monarchy of Lichenstein.
  • 1797: The Constitution. A square-rigged ship. Wikipedia lists plenty of other mid-late 1700's era ships.
  • 537: Hagia Sophia: Church in Istanbul, Turky. Is now a museum, but theres no reason it couldn't function as a church!
  • 300: Water wheels in Lijand China

Ancient tech still used:

  • Landscaping/terraces all over the world
  • Various bridges, roads
  • Irrigation canals, aqueducts
  • Can it be argued that the Egyptian pyramids are still functioning? I mean they are still standing!

Various things will definitely still be used. If we still drive on paths cut in the Roman times, apocolypse survivors will still use our highways.

Theory: If it has a use during the apocolypse (eg water wheels) it will probably be mantained by someone. If it's made of stone its not going very far very fast.

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    $\begingroup$ Most of these things either have expensive and extensive maintenance budgets, or are mostly big piles of stone in arrangements that won't fall over. $\endgroup$
    – Nepene Nep
    Sep 11, 2021 at 9:57
  • $\begingroup$ Idk if it makes sense to add "not so ancient tech in use" for equioment in use with no particular date but still in use, as an example on youtube is a guy - steam work shop - quite nice stuff there. Or have seen indonesia(?) steam powered mills(something, forgot) still maintaned and in use for harvest processing - was quite impressive, with videos on yt about it. $\endgroup$
    – MolbOrg
    Sep 11, 2021 at 15:48

Mostly recycle, with limited restoration.

100-500 years is a long time. It's long enough for concrete to break down for steel to rust, and electronic components to break. Some rare materials well repaired by nanites and protected from the elements may have lasted longer, but most of the technology is gonna be wrecked and useless to you.

  • $\begingroup$ What of the best case scenario which would be 100 years tops? $\endgroup$ Sep 11, 2021 at 9:14
  • $\begingroup$ That's enough time to wreck most structures, as noted above. Below 50 years is more the time frame when building materials are likely to survive. By 100 years stuff will be very gnarly. Also, apocalypses are rarely quick. Was the civilization really devoting their all to keeping their infrastructure perfectly intact in the years before they collapsed? $\endgroup$
    – Nepene Nep
    Sep 11, 2021 at 9:17
  • $\begingroup$ Nepene Nep I'd think that they'd be concerned with making it very durable given that they depended on it, I don't think that they'd dedicate their all to it, but I'd think it would be a major concern. $\endgroup$ Sep 11, 2021 at 9:22
  • $\begingroup$ Yeah, and we make very durable roads and bridges. But then they need to last decades or centuries, and maintenance budgets are very expensive. Things tend to get worse when money is short and chaos is high. If you are arguing because you want it to be realistic, you can just say their nanotech has magical repair properties and it did last this long. $\endgroup$
    – Nepene Nep
    Sep 11, 2021 at 9:24
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    $\begingroup$ @JuimyTheHyena You can check the condition of infrastructure in the USA as a reference. Maintenance is something that is often done poorly and not frequent enough (due to huge costs, no glory, and few political benefits). Unless nanotech has the ability to fully reconstruct the original materials it is reasonable to assume that no infrastructure will be maintained in a perfect condition. $\endgroup$
    – Otkin
    Sep 11, 2021 at 18:51

It depends on water.

mojave plane boneyard


Depicted: long term plane storage in the Mojave desert. It is dry. When there is water there is corrosion, and freeze/thaw heave. And there is life pushing and nibbling and burrowing.

Things in a wet climate return to the Earth fast. In a dry climate they can persist.

In your world, bone dry areas may contain buildings and relics several centuries old and still reasonably usable. In a wet area like New York City the team of life and weather will break down all but the Angkor Wattiest of objects very fast, and even those will be covered with plants.

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    $\begingroup$ I enjoy "Angkor Wattiest" as an adjective. $\endgroup$
    – jdunlop
    Sep 15, 2021 at 18:52

It may depend heavily on the societies' recollection, if any, of the fall. A society that venerates the old golden age before the fall will probably strive to rebuild their new civilisation on the bones of the old sites. A society that continues to remember the fall as a time of fear and chaos and the cities as the centres of the fall is likely to shun old places and build elsewhere.

There will be individual issues in certain areas with regards to emergent environmental hazards, I can foresee the following:

  • Based on the rate of decay seen at Pripyat many ferro-concrete buildings will become unsalvageable after only 20-30 years or so and be reaching final collapse around the 100-200 year era making city centres dangerous and unpredictable places to live and work.

  • Some areas contaminated with nuclear waste or certain chemicals, like DDT, will remain somewhere from unhealthy to unlivable for thousands of years and more. I don't even like to think about what will happen in places like the Umatilla Chemical Depot (that site has been decommissioned but others still exist).

  • Many industrial parks will have toxic contamination, particularly chlorine, that will take a minimum of decades to fade.

  • The bitumen used to surface many roadways worldwide is toxic and flammable potentially poisoning the soil for decades to come. It is also very useful and can be harvested, and melted down, for reuse.

  • Roads in general will be an obstacle to farming, the bigger the worse, as they will remain as a compacted layer under a thin new soil limiting drainage and root growth.

  • Copper from old houses worries me. Most suburban houses will burn down in the first decade after the fall. The wood, paper, carpets, plastics, etc... will go up in smoke or rot into the soil but the metals will linger, at least a bit. Zinc will oxidise in the fires and dissolve, mostly, harmlessly in the rain, Steel will rust, Aluminium and Stainless Steel will be retrievable from under the ashes for centuries to come, the Copper will slowly oxidise and dissolve into the soil. There-in lies a problem, unlike Zinc high levels of Copper oxides in the soil are damaging to plants growing in it and any animals that graze on them. This could create vast areas around the still standing ferrocement cores of the cities that can not support communities of any great size for many years after the fall.

  • Many waterways, especially in areas of intensive farming will be effected by agricultural chemicals leeching from the soil and leaking from storage silos, possibly for centuries, adversely effecting river ecology to varying degrees.


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