A paper mill is a factory that produces paper, usually using vegetable fibers or wood pulp. Other things often used include rags.
Dutch paper mill from 1654 in the Arnhem open-air museum
Stromer's paper mill, the building complex at the far right bottom, in the Nuremberg Chronicle of 1493. Due to their noise and smell, papermills were required by medieval law to be erected some distance from the city walls.