Imagine life inside a ring of cells around a central watchtower, where you can never be sure whether you are being observed. This surreal setup became an extreme reality under dictator Gerardo Machado on the Cuban Isla de la Juventud.

One of the creepiest concepts in the history of architecture, the Panopticon model of incarceration design proposes keeping prisoners forever on edge, fearing their watchers.

Both Fidel and Raul Castro spent time within the walls of this Presidio Modelo (Model Prison) complex, which, at its peak, held over 8,000 political prisoners. Apparently they found the approach sufficiently effective, since the Castro regime kept them open as well.

Originally the vision of Jeremy Bentham (and later nightmare of philosopher Michel Foucault), this 18th-Century idea was never realized in its creator’s lifetime but found expression in many structures after his death.  It was originally conceived of as an allegory for the surveillance state and something its critics never expected to be actually built – indeed, they would have been horrified to learn it had been physically realized.

While there are other Panopticon-inspired prisons around the world, this complex in Cuba may be the most literal and direction realization of the original diagrams. It features circular structures and guardhouses in the center of a vast open spaces, all to keep residents in a perpetual state of uncertainty (images via Jason Florio and Wikipedia).