The land-locked site at 9 Castlereagh St was chosen because of its close proximity to the company's old landmark "City Mutual Building" at 60-66 Hunter St. City Mutual wanted their new headquarters to be lavish, so no expense was spared in the building design.

This building’s design is discussed in detail by Harry Seidler in a 1993 lecture (synchronised with illustrations nos 13-24) recorded by UK architectural journalist Monica Pidgeon whose film archive is available online.

The building's lobby was refurbished in 2011 and won Australian Institute of Architects (NSW) Commercial Architecture Award Commendation 2012.

Some architects from the Seidler office saved the Utzon artwork from being destroyed (traced wall paint outline and removed the porcelain cylinders).

The Perry sculpture was later relocated to the building's entry lobby as part of the ground floor enhancements of 2011.