eli5: Why were some ancient cities like Palmyra and Machu Picchu left to ruin and fall apart over hundreds of years instead of being repopulated?

Question

eli5: Why were some ancient cities like Palmyra and Machu Picchu left to ruin and fall apart over hundreds of years instead of being repopulated?

In: 1677

Answer 1

Cities are really costly to maintain, and the benefits of a city only manifest when you have a thriving and advanced society. You need a ton of people *not* living in the city to feed the people in the city.

But they aren’t actually great for like… basic survival. So whenever you have any kind of societal collapse people tend to leave the cities first because they need to go grow food or something. That’s a lot easier to do in the countryside.

So the population of the city just falls and falls. And by the time said society recovers to the point they can maintain a city in the first place generally they have founded a new city that’s already thriving so there’s no point to move back anyway or they have lost the knowledge about how to maintain the cities infrastructure in the first place. Keep in mind it basically takes only a single generation for all the knowledge to be lost, even if you have written texts.

​

Another option is that the city is never fully abandoned, like Rome. But again, it’s so expensive to maintain that infrastructure that without a large enough population it falls into ruin. You even have people dismantling old building because they need to build something else. And for us it’s easy to go “omg how could you do that to something so important!” but like…dude needed those bricks to make a house so his family didn’t freeze in the winter.

Honestly, the same thing happened/is happening in the US rust belt.