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

Environment change is a big one (drought, combined with other factors such as land exhaustion and constant warfare is often cited as the reason behind the fall of Classical Maya city states); Lop Nor is another – a “lost” trading city on the Silk Road that was abandoned at least partly due to change in the course of the river.