Foundry Four, located beneath the surface of the planet Xorrn, was a warren of five separate underground droid factories created by the Geonosians, which were joined by a central . The facility had two main shafts located at each factory for moving raw materials and pushing out finished products. Each shaft ran 400 meters downward to a corvette-sized landing platform near a large cargo-staging area.
Above the factories was a of the gutted remains of several dozen Trade Federation core ships, left over from the Clone Wars between the Galactic Republic and the Confederacy of Independent Systems when the Republic ordered its sector fleet to initiate an orbital bombardment of the planet. To the west of the starship graveyard was the crash site of a derelict Republic Venator-class Star Destroyer from the war's end.
During the reign of the Galactic Empire however, the underground factories became home to a group of Galls in exile that had gathered their families and reopened Foundry Four, led by Lira Hardin. There, Hardin and her engineers could rapidly retool the assembly lines to create small batches of replacement parts and starship armament to order, which would then be used to refit civilian vessels in the Ferra Sector Shipyard in orbit and for later use by organizations like the Rebel Alliance, pirates and mercenary groups.