In Paris the visual effects of a polemoscope are so well known that no one dares bet on the real object of its gaze. Intrigued by this contraption, which allows anyone to gaze unobserved at anyone else, the famous adventurer Giacomo Casanova wrote a play of the same title. A diabolical little glass, one of his characters calls it. An opera glass, which is also a jealousy glass. Here you can play with this gadget in the way it might have been used in a theater, or a public space like a piazza, to spy on a lover or secret object of desire from a balcony or perhaps seated at the table of a fashionable café. You can play the game of the jealous husband, the policeman, the voyeur. But beware! You alone may think you are doing the spying, but someone else may be spying on you.