Slide showing a photograph of the General Post Office in Sydney. It is located at the western end of Martin Place. Designed by colonial architect James Barnet, the building was constructed in stages from 1866 to 1891. The clock tower was demolished in 1942 to reduce the visibility of the GPO in case of an air attack on Sydney. It was rebuilt in 1964.. Boswell Collection. Slide number 24. Sydney is the most populous city in Australia and the state capital of New South Wales. It is located on Australia's south-east coast of the Tasman Sea.