DMs: What's a bit of world building on the micro-scale you're proud of?

[MesiDoomstalker]

Sounds like a great hook for a horror/intrigue campaign.

Doomstalker's detailed explanation of how the twin-rivers affect the ecology and economy of the empire is the kind of stuff I love.

Thank you. I like to make sure, at least at a surface level, that my setting makes sense.