Fidel Castro called the building a “nest of spies,” routinely marshaling tens of thousands of people to protest at its doorstep. His government even made a television mini-series with what it called images of American diplomats lurking in a forest nearby, dropping off suspicious bags and marking benches in acts of espionage.
President George W. Bush took swipes of his own, installing a Times Square-style ticker on the building’s side to flash news and political statements. The move so enraged Cuban officials that they erected a thicket of 138 black flags on towering poles to block the sign.
Now the building, the American government’s main outpost in Cuba, for decades a hulking symbol of the tensions between the two countries, is supposed to become something else: a full-fledged embassy operating in the open for the first time in more than five decades.
Officially, the six-story embassy, in a choice spot along Havana’s seaside highway, was closed after President Dwight D. Eisenhower broke ties with Cuba in 1961. Yet it has hardly been dormant. Since 1997, the United States has run it as an “interests section” to process visas, hold cultural events and keep some communication flowing between the two estranged neighbors.
But all the while, it has also served as the staging ground for an on-again, off-again game of tit for tat — and spy versus spy.
“We were the closest of enemies,” Wayne S. Smith, who was the first chief of the mission in 1977, once remarked.
The exchanges have ranged from the serious, including the occasional expulsion of diplomatic officers, to the theatrical, especially when Mr. Castro was in power and made the interest section a rallying point to lacerate American policy.
For a generation of Cubans, the secret inner workings of the austere, concrete structure were supposedly revealed in the 1980s through a six-part series on state television called “The C.I.A. in Cuba.” It claimed to catch American officials in the act of spying, displaying briefcases, boxes and even a picnic basket for hiding radios that Cuban intelligence agents said had been given to them by C.I.A. handlers posing as diplomats.