In the midcentury the house at 2619 Wisconsin Avenue was attractive to all sorts of homebuyers: It had a big front porch, three stories, and was located in a family-friendly, residential neighborhood. Most attractive of all—to the FBI—it sat directly across the street from the Russian Embassy.

In 1977, the Soviet Union Embassy moved into a new building complex. It follows that, in the chaos of constructing the huge building, the FBI and the NSA would set up a secret spying station directly across the street.

According to most accounts, the house’s cover was negligible. The curtains were always drawn and no mail was ever delivered to the house, yet people were frequently seen coming and going. Cameras could be clearly spotted in the windows, filming all those who entered the Russian Embassy across the street. One local even reported seeing a long telescopic lens sticking out from a window late at night. In an attempt to up its anonymity, two FBI agents eventually moved into the house, though no one who knew of the house was fooled. The house’s owner was listed as “FBI” in public records, and its inhabitant’s occupation as “Clerk - really a spy.”

The FBI’s uses for the house may have gone beyond playing paparazzi. Operation MONOPOLY was a secret plan to dig a tunnel beneath the Embassy to record conversations taking place within the building, in the hopes of gleaning secret information. The problem was that the FBI had little knowledge of the Embassy’s layout. The agency hoped the tunnel would run underneath a conference or break room, but it was just as likely to lay beneath a storage closet.

The tunnel-digging was ill-fated from the start. Water regularly leaked into the tunnel, ruining the high-tech listening equipment, which rarely worked underground anyway. Though the FBI acknowledges the existence of the tunnel, they have never revealed which house in the neighborhood they began digging it from. Speculators believe it was either this observation house on Wisconsin Avenue or an abandoned house around the side of the Embassy on Fulton street. The truth may never be known for sure, as the tunnel has been sealed.