Edit- After reading most of the comments the general consensus is listed below:
1. The unique composite matrix of the concrete used gives it a self-healing property. When cracks form in the concrete, it will naturally seal them.
2. The Pantheon was a very significant structure which led to meticulous maintenance and restorations
3. The Romans didn’t have modern engineering. So they didn’t know exactly how strong they’d have to build the Pantheon to make it last. Their solution was to overbuild the hell out of it.
4. Survivorship bias. There were thousands of buildings constructed by the Romans but very few remain which are the ones we marvel at.
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In: 564
I used to wonder why ruins didn’t have lots of stone lying around. Like, the building fell down, where’s the rest of it? Turns out most ruins are ruins because people chipped away the stone to use as building materials. Not because they fell down.
The Colosseum, for example, only still exists because the Popes saw it was being chiselled away and forbade anyone to do that.
Short of a massive earthquake, or pillaging, stone structures are going to stay standing for thousands of years. The aqueduct at Nimes is in great shape, probably because no one has ever wanted to build anything close enough to it to make it worth taking apart.
There are a lot of reasons for this exact situation but it’s important to remember that we can make things last longer, it’s just that one thing(building or something else) that lasts a long time is worse for gdp than many of those things being sold
Do you peeps mean the Parthenon?
Nobody seems to mention this.
The biggest component is Rebar.
Our modern concrete is *significantly* better than Roman concrete because of reinforcement. The cost of this is that the iron rusts, and as it rusts, it expands, and as it expands, it cracks the concrete, which lets it rust more, which causes the death spiral.
Modern concrete is only supposed to last ~50 years because of a design decision. We would be more than capable of building a building that will last 2000 years, that’s just never a design requirement.
The Romans also tended to over-engineer the hell out of things (so did we until computer modeling allowed us to get a better idea of how strong things actually needed to be)
I think a bit of it is survivorship bias, if I have built 1000 buildings, and 10 of them are left standing 2000 years from now, that means 1% are still standing and 99% fell, doesnt seem that unrealistic. Some buildings will leave a better foundation by chance, some will not get hit by an earthquake etc. But we look at the 10 buildings that are still standing and be amazed.
Survivorship bias – plenty of big beautiful ancient buildings didn’t survive. Only some did. There are plenty of modern buildings that would also last thousands of years.
Maintenance – A lot of work has gone into restoring/conserving important structures like that over time.
The Romans built *lots* of buildings. Some of those were important to them, so they repaired them when they needed it. Buildings like the Pantheon (literally “temple of all gods”) and the Coliseum were maintained regularly. Other buildings were not, but we don’t see those today, because they wore out and were demolished for materials to build other stuff.
The Romans made really good concrete, and that helped, but the biggest thing is the regular maintenance. We could probably keep a building in pretty good shape for thousands of years if we wanted to. I would imagine the US Capitol and the White House will be in pretty good shape 2000 years from now, if the US still uses them as important government buildings. Other buildings, like any random house, will not be in such good shape.
One key reason that Roman concrete lasts millennia but modern concrete lasts 50-100 years typically is that most modern concrete is reinforced. Reinforcing concrete dramatically reduces its lifespan because as the iron corrodes it warps and expands which compromises the structural integrity of the concrete
They recently discovered that they had lime clasts in their concrete that gave the material a sort of self mending effect. Interesting and could be why some of these structures still remain [an article on it](https://greekcitytimes.com/2023/01/07/ancient-roman-concrete-could-self-heal-thanks-to-hot-mixing-with-quicklime/)
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