Samuel Bentham brought the idea from Prince Potemkin's Russia; Jeremy designed the inspection house around 1791: a circular cell block around a central tower, inmates visible always, inspectors visible never, conversation tubes for direct address. Bentham's own scope was total: prisons, schools, factories, poorhouses, asylums, any institution where people need observing. No true panopticon was built in his lifetime; near-versions stand in Italy and the Netherlands. His goal, stated in writing: control of the mind rather than the body.
Foucault's Discipline and Punish, 1975, promoted the building to metaphor: the diagram of a mechanism of power reduced to its ideal form, where visibility is a trap, the inmate internalizes the gaze and becomes his own guard, no coercion required. His examples were schools, hospitals, factory floors, city grids; the digital age finished the job: CCTV, tracking, wearables, feeds, and the self-curated profile, the prisoner now pays for the cell and photographs himself for the tower.
The claim: the Panopticon's deepest trick is that the inspector is optional, power survives as pure architecture of possibility, so proving the tower is empty changes nothing, and every expose of surveillance that leaves the structure intact merely confirms to the watched that the tower exists. Verdict: this is Foucault's actual point, and it explains the archive's own pattern: the Guardian Angel, Main Core, and Carbyne files all describe towers whose occupancy is undecidable by design. You cannot check the tower. That is the tower.
If the tower might be empty, does it matter whether anyone is watching?