Comment by fredley
5 hours ago
> To William’s complete lack of surprise, the little cellar under the shed was much better built than the shed itself. But then, practically everywhere in Ankh-Morpork had cellars that were once the first or even second or third floors of ancient buildings, built at the time of one of the city’s empires when men thought that the future was going to last for ever. And then the river had flooded and brought mud with it, and walls had gone higher and, now, what Ankh-Morpork was built on was mostly Ankh-Morpork. People said that anyone with a good sense of direction and a pickaxe could cross the city underground by simply knocking holes in walls.
For a modern example, see the Raising of Chicago: https://en.wikipedia.org/wiki/Raising_of_Chicago. I think I've seen an image of what the old ground level looks like now, and / or that you can take tours there. There's probably loads of stuff buried there now.
Edit: Actually it was Seattle, you can still visit its old ground level: https://en.wikipedia.org/wiki/Seattle_Underground
My understanding of the Chicago case is that most of what the old "ground level" was is just sewers today. I heard some of it was railroad tracks and maybe some are still used for cargo-only trains, but most of Chicago wasn't really raised a full "floor" with enough headroom for interesting underground spaces.
A US city often overlooked for some intricate people explorable underground spaces is Cincinnati: https://www.visitcincy.com/blog/post/unmistakably-cincinnati...
Some of Cincinnati's underground exists from plans to build subway trains that never completed. I think that makes Cincinnati's particularly sad being that it constitutes a perpetually unfinished public works/public transportation project.
Relatedly to that, Atlanta also has a tiny underground leftover from passenger train lines that ended passenger travel decades ago (and so was turned into a mall, because America): https://en.wikipedia.org/wiki/Underground_Atlanta
https://futurama.fandom.com/wiki/Old_New_York
... was once New Amsterdam