Eli5: How do newer cities get built over more ancient cities?

Question

I hear about archaeologists finding layers of old cities below newer ones. My brain can’t make it work. I keep imagining an Amsterdam or a Chicago, decaying, then just building atop it?

In: 14

Answer 1

Chicago is an example. They raised the streets many years ago.

https://www.choosechicago.com/blog/architecture-history/underground-chicago-the-layers-of-our-city/