Liberation newspaper, one of the publications that revealed the spying claims, suggested the building is home to secret rooftop spy station hidden behind a canvas, with fake windows painted on it.
It might seem too simple to be true but according to Liberation this is where the US intelligence services snooped on communications from the Elysée and various ministries, all located nearby.
Concealed behind the canvas, which allows electro-magnetic signals to pass through, are a number of antennas that can pick up phone conversations in the vicinity, Jean-Marc Manarch, the Liberation journalist behind the claims, said.
The spying den was installed back in 2004/05 during work on the roof of the embassy, the paper claims.