Property tycoon Harry Stamoulis has bought the One Collins Street tower complex at the top of Collins Street, Melbourne, for $125 million.
It was bought from fellow BRW rich lister Robert Magid and his sister, Nora Goodridge.
The complex comes with 17-storey modern tower overlooking Treasury Gardens and an 1870s heritage residence that served as Australia's first war cabinet room in 1914.
The Australian Financial Review says it was struck on a tight 5.25 per cent yield and at a high building rate of more than $9000 a square metre for the fully leased A-grade office complex.
The Australian says it was sold by Knight Frank.
Rabobank, Mckinsey & Co, Grant Samuel and IBISWorld are tenants at One Collins Street.
The Magid family acquired it for $43.1 million in 1997.