What does a city smell like at 4am?

I was walking back from the station last night, and the air had that particular stillness—no traffic, no coffee steam, just damp concrete and the faintest hint of old laundry from an open window. It reminded me how much I’ve forgotten about the sensory grammar of cities when they’re not performing for tourists or commuters. What’s your 4am city? Not the one in the guidebooks, but the one that smells like cold metal, wet paper, and something unnameable that only shows up when everyone else is asleep?