What does a city smell like at 5am?

I was walking back from the station last week, and the air had that damp concrete-and-diesel haze you only get when the world’s still half-asleep. I stopped to breathe it in—something between old newspapers and wet wool—and thought: this is what a city sounds like if you could taste it. Not the tourist version, not the postcard one. The real one. What do you notice at that hour? I keep wondering if anyone else pays attention to those quiet, fugitive scents.