The Mill

 is a building in The Pitt, added to Fallout 3 in the DLC pack The Pitt. The steel mill also contains The Hole and the Ammo Press which according to Ashur is how he has kept his "army" intact and with ammunition "all these years".

Behind the scenes

 * In the real world, steel mills were never located in this part of Pittsburgh. They were located along the banks of rivers opposite from the Downtown area, such as the same side of the river as where you emerged from the tunnel.