The Russian embassy now was the Soviet embassy..........they put it on one of the DC's biggest hills...............why??  Better for electronics..........sending messages................trees interfere with communications...........esp. back then..........trees or hills..................etc........

A Not-So-Secret Tunnel - CBS News

https://www.cbsnews.com/news/a-not-so-secret-tunnel/

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Mar 4, 2001 - The United States built a secret tunnel under the Soviet Embassy in Washington, but investigators believe the operation was betrayed by the FBI agent accused of spying for Moscow, according to a New York Times report. This operation, which current U.S. law enforcement and intelligence officials ...

Embassy Neighbors Try To Dig Up Dirt on Tunnel - The Washington Post

https://www.washingtonpost.com/.../embassy...tunnel/a50e6d5a-0cf5-4060-ab1f-f5b3...

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Mar 11, 2001 - On the other side of the far wall is the dirt of the hill sloping into the Russian Embassy compound. Like everybody else, Oberschneider learned last week that the FBI had built a secret tunnel to eavesdrop beneath the then-Soviet Embassy on Wisconsin Avenue NW. Oberschneider's first reaction was anger ...

Operation MONOPOLY · International Spy Museum

https://www.spymuseum.org/education-programs/news.../operation-monopoly/

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In 1977, with embassy construction proceeding above ground, the Bureau and the National Security Agency (NSA) launched operation MONOPOLY—digging an underground tunnel to eavesdrop on unwitting Soviet diplomats