A PENTHOUSE in the Sydney suburb of Potts Point has sold for $20 million - setting an Australian record - and it hasn't even been built. While half of Sydney's property values slide backwards, the eastern suburbs continue its unabated boom with the uprecedented sale. Sold "off-the-plan", the two-floor unit with views of the Harbour Bridge and Opera House is expected to be worth even more once it is completed at the end of 2009. The $20 million price tag smashes the country's previous record for a unit sale of $18.2 million, set last year by a sub-penthouse in East Melbourne's Mercy Hospital redevelopment. Sydney's previous record of $16.75 million was set in March by a 12th floor penthouse in the "Toaster" at Bennelong. Potts Point selling agent Geoff Cox couldn't be drawn into saying who the mystery buyer was, but it is understood to be a prominent Sydney businessman. The penthouse, spanning the top two floors on levels five and six, has 270 degree views of the CBD, 531 square metres of living space, 115 square metres of balcony, and parking for four cars. Ashington Apartments executive director Craig Minahan said the building would have 10 luxury apartments with interiors by fashion designer Alex Perry. "We expect to draw interest from a range of buyers including affluent professionals seeking proximity to the city, empty-nesters looking to down-size from larger family homes, local residents looking to upgrade and expatriates looking for a Sydney base," he said. Construction is scheduled to begin in August.