Giovanni Battista Piranesi’s series of prints called “Imaginary Prisons” are fantastical studies of great underground architecture, confusing labyrinths of staircases and arches, which at first glance appear realistic, but the more you study them, the more impossible they become.

The Round Tower,” c. 1749

Prisoners on a Projecting Platform,” c. 1749

The Gothic Arch,” c. 1749

The Drawbridge,” c. 1749

The Pier with Chains,” c. 1749