Agote and Gainza, both graduates of the École Centrale des Arts et Manufactures, drew from their training in Paris to create a Beaux-Arts design, beginning with a façade inspired by French architect Charles Garnier.
The Beaux-Arts exterior is notable also for its spire, which is topped by a gilt bronze monument to freedom of the press represented by Pallas Athena and created by French sculptor Maurice Bouval (of Thibaut Frères).
The siren has been rung five times over the decades: on news of the assassination of Umberto I, the King of Italy, in 1900; on the landing of the Apollo 11 spacecraft on the Moon; on the Argentine National Football Team's first FIFA World Cup, in 1978; on the invasion of the Falkland Islands by the last dictatorship, in 1982; and on the return of democracy with the inaugural of President Raúl Alfonsín, in 1983.
The building's interior was completed with mostly imported materials, including Spargne elevators from the United States, as well as French fixtures such as Boulanger mosaic tiles, clocks by Paul Garnier and wrought-iron work from Val d'Osne.
The first floor is centered on the Golden Salon, where Paz opened the Popular Conference Institute, celebrated during the twentieth century for its weekly literary readings and lectures (notably those of Jorge Luis Borges).