Generally acknowledged as Australia’s first major office tower, Australia Square (1968) was designed by archi-phenomenon Harry Seidler. His 50-storey design assumes a distinctive cylindrical form, with an open plaza at the base and shops below. A vibrant Sol LeWitt lobby mural (2004) replaced a rare Le Corbusier tapestry that hung here for decades before the building’s owner auctioned it off. Head up to O Bar on the rotating 47th floor – jaw-dropping views for the price of a martini.