One example offered by Price of how space and surveillance overlap is the panopticon, a concept but forth by philosopher Jeremy Bentham, where prisons would be circular with a single guard tower in the middle with one way glass so that many prisoners could be watched by one guard but that the prisoners would not see the guard. Foucault later noted that the point of how the panopticon is designed was not that the guard could be watching all prisoners, but that the prisoners never knew if they were being watched so the space of the panopticon would lead to prisoners self-surveilling their own behavior.