[DISCLAIMER: This question is super pedantic and I acknowledge the name of the zone is canonically Hydro City. Not trying to ruffle feathers, just curious.] Something that's always bugged me about Hydrocity v. Hydro City is that it's never felt like a city to me. I don't think we see dwellings or anything, it's kind of an aqueduct with massive candles and sculptures which could (I guess?) be a very slight religious lean. Thoughts?
I mean, we never really see dwellings in Classic Sonic, period. There’s maybe one zone per game that looks like it might be borderlining on a livable space, but mostly it’s not.
But look at Aquatic Ruin. It’s all pillars and stone structures but there’s no windows or anything. What’s it for? Do people live there? You could say maybe it’s an amphitheater or a market of some kind, but again, no indication. It’s a bunch of greco-roman stuff in the middle of a pond.
Fact of the matter is, I’m pretty sure Hydrocity is the only Sonic stage with the word “city” in it. Those might not be homes in Starlight Zone, or Chemical Plant, or Casino Night.
Aqueducts aren’t usually enclosed underground, as far as I know. And if they are, they are usually more commonly referred to as a sewer, or a pipe. That’s something more along the lines of, say, Labyrinth Zone or something. Hydrocity seems to contain aqueducts, but it in itself is not an aqueduct.
Maybe we could ask ourselves where all this water is coming from and where all of it is going. I suppose you could say it’s runoff from Ice Cap Zone. Maybe it’s summer, and some of the ice is melting. At the end of Act 1 we can see a river in the background carrying sheets of ice somewhere. Presumably to Hydrocity, we could imagine.
But given the large volume of water in Hydrocity -- more than any other stage in Sonic 3 -- it does seem like that’s where a lot of it is meant to stay, for the most part.
Though now I wonder if the huge waterfall(s) we see in Angel Island Zone aren’t runoff coming out of Hydrocity. But, then, I suppose if you have ice melting, eventually lakes and things will overflow and the excess has to go somewhere. Hydrocity may store large volumes of water, but it cannot store infinite water.
Technically, it could, though. Someone built this huge network of waterways and pools but they left a lot of open space. It’s not purely a storage tank. Somebody deliberately carved out space for open are traversal. That to me says people are meant to exist there. It’s not purely ancient-industrial. Which could mean a city. People (or other creatures) could live there, somewhere.