How the Pantheon, which was built over 2000 years ago, is still standing when buildings made 150 years ago are about to crumble.

Question

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

Answer 1

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.