The CB3 building is currently undergoing restructuring, led by WO2 and designed by the firm Ateliers 2/3/4/. Unoccupied since 2016, this office building is being transformed into a low-carbon model. In the future, it will offer 34,400 m² of office space and 2,800 m² of outdoor space. By aiming for a low-carbon construction, using bio-based materials, for example, it will become the first building in La Défense to aim for the Excellent level of the Low Carbon Building (BBCA) Renovation label.

The CB3 building, formerly known as SGAM, was built in 1978 and renovated in 2006. In the 1980s, the architects who designed the project, Roger Saubot, François Jullien, Skidmore and Associates, went against the vertical logic of the business district and built a 30,000 m² complex (equivalent to a first-generation tower, no more than 37 m high).

Despite its horizontality, the building is in line with the agency's other projects, with its glass facades, silver aluminum profiles, and dark blue spandrels.