'The Forge'

All I know is a door into the dark.
Outside, old axles and iron hoops rusting;
Inside, the hammered anvil's short-pitched ring,
The unpredictable fantail of sparks
Or hiss when the new shoe toughens in the water.
The anvil must be somewhere in the centre,
Horned as a unicorn, at one end square,
Set there immovable: an altar
Where he expands himself in shape and music.
Sometimes leather-aproned, hairs in his nose,
He leans out on the jamb, recalls a clatter,
Of hoofs where traffic is flashing in rows;
Then grunts and goes in, with slam and a flick
To beat real iron out, to work the bellows.

Seamus Heaney - Door into the Dark, 1969.