An electronic screen perched on the fifth floor of the six-storey US Interests Section (USIS) in Havana projects messages in crimson letters more than a metre high.
On Monday and Tuesday it began broadcasting the UN Declaration of Human Rights, the thoughts of US civil rights leader Martin Luther King Jr and the latest news, to surprised passers by on Havana's seafront.
Unsurprisingly the Cuban leader Castro did not welcome the screen with open arms.
Speaking on state television on Friday he said: "I must analyse the provocations, the outlandish things (US authorities) are doing."
The USIS said in a statement: "it is here to stay. We are trying to provide the Cuban people uncensored information. The intention is to break the news embargo Cubans are subjected to."
The screen, however, was not turned on Wednesday and Thursday.
Castro, 79, also claimed the United States was "planning to break the migratory accords" agreed with Bill Clinton's government, but did not provide any further details.
The accords are central to the neighbours' tense bilateral ties. They stipulate that any Cubans trying to emigrate to the United States who are picked up at sea by US authorities are repatriated to Cuba.
The new lighting fixture is the latest US effort to draw Cuban public attention to what the United States sees as human rights concerns in Cuba. The former top US diplomat in Cuba, James Cason, started the campaign in 2004, which has been expanded by his successor Michael Parmly, who took over at the USIS in September.
Rice is not the first US official
to get a Castro tongue-lashing
The United States and Cuba do not have full diplomatic relations, but maintain interest sections in each other's capitals.
Washington has had a full economic embargo on Havana since 1961.
Castro has recently launched several attacks on senior US diplomats, using language considered strident even by his standards.
On 23 December he called US Secretary of State Condoleezza Rice "mad" after previously labeling Parmly as a "little gangster".
Castro's tirade against the US followed Rice's meeting last month with a US government commission intended to prepare for a democratic transition in Cuba after Castro.
Castro told the Cuban parliament: "I am going to tell you what I think about this famous commission: they are a group of shit-eaters who do not deserve the world's respect. In this context, it does not matter if it was the mad woman who talks of transition -it is a circus."
The attack followed Castro's comments a day earlier when he attacked Parmly for criticising the regime at a speech marking International Human Rights.
Parmly said: "The Cuban regime's hurling of angry and often violent groups against pro-democratic dissidents is particularly disgusting," adding that such actions recalled the Nazis.