Outside was a corridor, walls, floor, and ceiling made of sandy stone, with metal support girders. (Not actual stone, but an artificial building material that looked like it.) Round light sources studded the girders at intervals but there was no power. The drone followed it out to a foyer with a taller ceiling, with round windows set high in what had to be an outside wall, letting in gray daylight. Racks and cabinets and an unused workbench lined the other walls. A thin layer of dust on the floor said this area hadn’t been disturbed in a long time, and also indicated that somewhere in this structure was an opening to the outside where there was actual dirt. The door wasn’t a pressure hatch, it was a manually operated metal sliding door.