"hellll yes infinite procedurally-generated city" is the title of the Trello card left in the RPS organisation-o-tron 3000 concerning Wave Function Collapse, and yep, that neatly sums up what I want to say about this.
An endless city, one of a kind, created just for you whenever you load the application. Close the application, and that city's gone forever. Maaaaan.
While all is alabaster in tone and there are only so many different architectural building blocks to call upon - i.e. each city looks aesthetically similar, even if the layout is unique - it's impossible not to be thrilled by this. These vast 3D spaces, all tunnels and stairs and fountains and spires and balconies, all yours and yours alone to scale and explore. It's pretty generous with its jump height too, so there's even a touch of the AssCreeds to it, without all that nasty fighting and storytelling business.
(Or you can switch to flight mode by pressing M, but that's not as impressive or satisfying as traversing it all yourself. And by 'all' I mean a tiny, tiny fraction of a place without end).
All the more impressive is that this was originally made as a submission to Procjam, the procedurally-generated gamejam, rather than being the work of aeons.
It's the work of a German dev calling themselves Marian42, and there's some fascinating detail on how and why it was made here. And, over in comments on the Itch page, it's revealed that a city can in fact be exported for use in other projects. Which is an exciting prospect in and of itself.