This has been going on since the dawn of civilization.

Basically each generation/civilization built ontop of the previous structures. Many roman churches and government buildings were built on top of pagan sites of importance for example.

I guess even the great pyramid was built ontop of some kind of old structure which was built ontop of a natural spring or something. Interesting for sure.

I guess mexico city right now is facing a once in a generation drought.

When they showed up in what the 14,1500's? The indians had a city where mexico city is at, but it was built with a bunch of canals and reservoirs. The spanish demolished this when they needed to expand their city.

They proably thought the indians were retarded and built it for "looks" but they likely built it for the once in a generation droughts like these.

And since they built the entire city on a what is now a empty lake, the city is sinking something like 20 inches per year, yikes.