During the Cold War, divided Germany and the GDR, in particular, were important operating areas for Western intelligence agencies. Their goal was to gauge the military strength and technological progress of the Soviet Union and its Eastern European satellite states in order to better predict their intentions and capacities. “Operation Gold,” which was carried out between May 1955 and April 1956, took aim at the Soviet communications network. The American CIA and the British SIS dug a 500 meter-long tunnel from the American sector into the Soviet sector, where they tapped into three important military telephone lines. For eleven months, these Western intelligence agencies were able to receive information about military armaments, politics, and military espionage. The Soviets, however, had a double agent in the SIS, and had known about “Operation Gold” since its planning in 1954. But they were unwilling to endanger their double agent, so they waited until April 1956 to stage a “coincidental” discovery of the tunnel. This photograph was taken during a public viewing of the tunnel for East Berlin residents. The official caption by the GDR news agency ADN read: “This USA spy tunnel is presented for public viewing. On May 3, 1956, the USA spy tunnel in Berlin-Altglienicke was opened for public viewing. Members of the public can see with their very own eyes this criminal attack by the Americans. [ . . . ]”