Breath of Iron

I am a lock, iron that holds the night.
The city crosses me with the breath of dawn.
Every key dances, and the sigh enters or stays within.
I count the steps, breaths fixed in my metal.
Who enters brings new wind, promises and scents.
Who stays ignites silences and trembling lights.
I decide whether to let you pass or remain, according to their heart.
Thus the breath of the city flows through me, guardian and witness.