Aerial view of the 50 storey tower occupying only 1/4 of the site

Replacing a city block of 30 different amalgamated old properties, this is Sydney's first tall office tower built due to the foresight and energetic enterprise of the Dutch immigrant developer, G.J. Dusseldorp.

The 50 storey circular tower occupies only 25% of the site with a total floor space of 12 times the site area. The remainder of the city block was given over to the public; newly gained useable outdoor space, with trees, a fountain and outdoor restaurants.

Curved screen walls that are raised, separate the space visually and physically from traffic and parked cars in the surrounding streets. It is an area for people to linger and relax, attracting large lunchtime crowds.

Structurally the circular form of the tower is most efficient in resisting horizontal wind loads. The light weight concrete building is 42 m in diameter with a clear span of 11 m from core to perimeter. This configuration lends itself ideally to speedy repetitive and mechanised component construction. Every elevator shaft, every radial beam and column are identical. The projecting columns diminish in size as the building rises.

Gross to nett space efficiency is 80-20 percent. Each floor was erected in five working days.

The tower with Alexander Calder's steel sculpture

Interlocking rib structure supporting heavily loaded exhibition floors and typical radial upper floor beams

Rib structure of 'ferro-cement' by P.L. Nervi