Fungi in the subway is a thing in Stockholm's subway too, discovered in one station in back 2016 [1].

[1]: https://en.wikipedia.org/wiki/Kungstr%C3%A4dg%C3%A5rden_metr...

Made me instantly think of this: https://www.nationalgeographic.com/science/article/slime-mou...

Something ironically self-referential about not only fungi growing (like) rail networks, but also IN rail networks.

Is there a slight 'Last of Us' motivation here?