Ask HN: What's the most beautiful code you've read?

Hi everyone! For a long time with friends I've discussed the idea of reading code like literature. It's interesting to me that there doesn't seem to be much culture around this practice even though actually working as a software developer often involves more reading than writing.

I just started working at an organization which helps high schoolers run coding clubs around the world and was thinking of ways to help people appreciate the aesthetics of code. I'm thinking of trying to organize some "code reviews" that work almost like book clubs and am trying to find good material, so I thought I'd ask you!

What's the most beautiful code you've read and why? It can be a snippet or a whole repo. I'd love a little explanation as to what you like about it, or how it changed the way you think. Thanks!