Here are some panoptican images from the island Isla de la Juventud in Cuba where Castro became imprisoned and later detained his enemies. The structure, although now crumbling, has a very menacing atmosphere. You can see the guard tower in the centre where a watchman with a gun would enter through a passage underground. This means that the prisoners do not when when the guard is present and cannot see which direction they face. This means that the prisoners begin to self-regulate behaviour in the highest of utilitarian efficiency. The greatest amount of control by the smallest amount of effort.