 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 m ³ , constructed from 4 @,@ 600 tonnes of steel frame with brick infill and floors constructed of hollow blocks to provide over <unk> m ² of usable office space " . The façade is clad with 33 @,@ 000 m ² Stuttgart @-@ Bad <unk> <unk> 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 . 
