The Ellipse building, as its name suggests, has a quarter-circle layout, combined at the rear with a semi-pyramidal volume allowing the north-facing offices to enjoy daylight. Built in 1974, the building underwent a complete renovation in 2000, acquiring a fully glazed façade. This curved façade integrates it into the urban continuum of the La Défense office complex, establishing links between the district and its immediate surroundings.

Grison, Moritz, and Ristorcelli is a Swiss architecture firm founded in 1999 by François Grison, Fabrice Moritz, and Philippe Ristorcelli. Since its inception, the firm has worked on a wide variety of projects, ranging from the renovation of historic buildings to the design of towers. All of their projects combine modernity, functionality, and attention to detail.

In 2000, Ellipse was completely restructured by Jean Hanemian, known for his modernist designs and his contribution to 20th-century French architecture. Among his most famous achievements are the library of the Arab World Institute in Paris, the L'Oréal headquarters in Clichy, and the Les Olympiades office complex. His contribution to French architecture has been recognized with numerous awards, including the Grand Prix National de l'Architecture in 2008.