Indagare Nogitsune
Adventurer
When people don't comment it's hard to know, but I appreciate all the viewsYou've gotten 898 views on this, so I think there's more than two people tuned in - others are probably lurking, waiting to see how this gets fleshed out or cribbing notes.
One of the things I've been thinking about is a Fire Rift; we have the other three, could there be a Fire one, perhaps suppressed or not well-known to protect the city from being burned down by careless individuals? It could be of benefits to keeping the city warm in an otherwise wintry clime, mined for live coals or manipulated for forges/hearths and the like. Perhaps it was sealed long ago, and the ancient portal lies in the deep caverns beneath the city, protected by ancient guardians or under the stewardship of a cult who wants the city burned down (figuratively as well as literally). A "fire brigade" rebellion or criminal ring would be interesting; a protection racket of "pay the fire god or he'll visit your establishment" sort of crime syndicate.
As Brendan Byrd pointed out, Hackwark is where the Fire Rift is, opposite the Water Rift in Waveswith. It is very useful for both heating and smithing and may or may not have had something to do with the Great Burning. It most likely has a lot of protection, especially since the crime syndicate you mention certainly could have existed (or still exist in different form).
In my head, the Modern City would be very Metropolis, the Noir City would be very Gotham and the Victorian City would be something like the various novels Sherlock Holmes, Around the World in 80 Days, 10,000 Leagues Under the Sea, Journey to the Center of the Earth, and War of the Worlds among them. I'd argue Girl Genius too, but that would make the weird stuff of the future need to be weirder than the stuff of the past and that's a lot to ask from something based on that series.