In 1928, IG Farben was the world's fourth-largest company and its largest chemical company. Consequently, the space requirements for the building were for one of the largest office buildings ever constructed. It was designed in the New Objectivity style. The 250-metre long and 35-metre tall building has nine floors, but the height of the ground floor varies (4.6–4.2 m). This variation is reflected in the roof line which looks taller at the wings than the spine. The volume of the building is 280,000 m³, constructed from 4,600 tonnes of steel frame with brick infill and floors constructed of hollow blocks to provide over 55740 m² of usable office space". The façade is clad with 33,000 m² Stuttgart-Bad Cannstatt Travertine marble, punctuated in bands of windows decreasing in height with each storey. Only at the corners are the glazed strips interrupted for emphasis. The top storey is lit from skylights rather than banded glazing and has a very low ceiling height. It forms a clear building conclusion. Until the 1950s, the building was the largest and most modern office building in Europe. The IG Farben Building consists of six wings, connected by a gently curved, central corridor. This arrangement provides all of the offices with sufficient natural light and ventilation. This design approach for large complexes offers an alternative to the "hollow rectangle" schemes of the time, with their typical inner courtyards. The prototype of this form is the General Motors Building in Detroit (1917–21) by Albert Kahn. The building presents a very large and weighty façade to the front, but this effect is reduced by the concave form. The main entrance is at the axial centre of the building, comprising a temple-like portico standing in front of the doors—a relatively common motif of administration buildings of the time. The entrance arrangement is regarded by some people as slightly pompous: the entrance and lift doors are of bronze, and the ceiling and walls of the porch are clad in bronze plate and copper friezes. The inner lobby has two curved staircases with a sheet aluminum treatment, and marble walls with a zigzag pattern. The axial centre at the rear of the building has a round glazed façade; here, the view of the buildings at the rear of the site (the "casino") is maximised by the curved walls that afford vistas to the subsidiary buildings 100 m distant, separated from the main building by parkland and a pool. During the American occupation of the building, this rotunda housed a small kiosk; later, it was used as a conference room. Nowadays, it is called the Dwight D. Eisenhower room and accommodates a café.