Central California, especially near Visalia, smells of poop. I suppose that's fertilizer for the farms.

I drove past some pig farms in North Carolina once, and that smelled bad, but it didn't seem as bad as central California (pig farms have a more natural poopy smell ).

When I was a kid, sometimes you couldn't go outside at Lake Cherokee in east Texas unless you wanted a whiff of camera film byproducts from the Kodak factory (seriously, it smelled exactly like camera film). I haven't been there in a while, so maybe it's not as bad, if there at all, given the huge increase in the availability of digital cameras.