German artist Simon Menner spent more than two years pouring through the Cold War-era archives of East Germany's secret police. His search turned up all kinds of formerly secret images, collected in his book Top Secret: Images from the Archives of the Stasi. These photos show the details of the Stasi's vast surveillance operation, from seminars on disguises to a manual of combat techniques to Polaroids of apartments about to be ransacked.

Some of the photos seem goofy and absurd: Agents wear fake moustaches and crooked wigs. They use a secret sign language that looks like a game of "Simon Says." In their spare time, they dress up as dissidents for costume parties. But the unglamorous images reflect the pervaseness of the Stasi's vast surveillance aparatus, which at its height employed more than 100,000 spies: "For me, the banality of these images makes them even more repulsive," Menner writes.

From a training seminar on disguises:

Practicing the application of their faux facial hair:

From a seminar teaching secret signs to new agents:

From a manual on combat techniques.

Fom a high-ranking official's costume party. Agents dressed up as groups—priests, atheletes, peace activists—under Stasi surveillance.

From an unconventional award ceremony:

A spy selfie:

Surveillance photo of a bedroom of a teen with alleged pro-Western sympathies: