The complex consists of an L-shaped tract and a terraced volume, with an atrium between the two that acts as a thermal buffer. The visual focus of this space is a spiral staircase. Its slender steel steps, perforated balustrades and raking, branching members suggest a delicate, plant-like sculpture. In the terraced tract, a straight-line concrete staircase sweeps upwards through all five storeys of the building, attached to the side walls solely via the landings. Dan Flavin’s lighting installation on the underside bathes this white space in an unreal light and relieves the stairs of their massive quality. The spaces between the stairs and the walls create a sense of vertical continuity and allow the light – a different colour for each floor – to radiate upwards.