Four office towers, built in the 1980s, have been refurbished and reglazed. The ground and first floor levels, together with peripheral areas, have been reconfigured to create a sequence of spaces enclosed by an extensive glazed roof, over 190m long and 90m wide. The spaces include an atrium, a piazza, a four-storey timber-clad office space, a 7m-wide, three-storey-high pedestrian street, and a shopping arcade.
The enclosure is designed as a buffer zone, with natural ventilation and underfloor heating. At the glazed east facade, which incorporates the main entrance, the roof is more than 20m high; it slopes gently over the enclosure to terminate in a 7m high canopy above the east facade.
The roof consists of clear double-glazed units - a 10mm toughened outer and 8.8mm laminated inner sheet for safety. Inset gutters run between the units at 3.6m centres, directing rainwater to a syphonic drainage system.
The roof rests on two series of steel trusses: canted 'fin' trusses, which run below the gutters and are sheathed in polyester powder-coated aluminium fins to clarify the structure and emphasise the curved form of the roof; and transverse trusses, which run in the opposite direction to connect them. The fin trusses are formed of 152 x 152mm UC members and 168mm diameter CHS top booms which support the gutters.The transverse trusses are formed of CHS members with forked connectors at their ends, which connect the trusses with plate connectors and cast steel nodes.
The trusses are supported at 7.2m centres by a series of tree-like structures.Each consists of three 127mm diameter CHS struts branching from a circular column.