While the community of Australian planning professionals is familiar with the identification, interpretation and application of heritage conservation areas, this is not a concept that is familiar to the general public. Yet, none of the official publications issued by the New South Wales state heritage authorities provide a definition of the purpose of heritage conservation areas that goes beyond the declaring them to be a spatially bounded area containing heritage items. It is left to the local planning authorities to provide their own interpretations and definitions. This paper provides a systematic review of the definitions contained in NSW local heritage studies and planning documents. It presents the first ever comprehensive definition of the purpose of heritage conservation areas as well as of the nature and characteristics of an area’s constituent, contributory or detracting components. Based on this, the paper then explores the role of heritage conservation areas as part of the public heritage domain focussing on the importance of isovists and commensurate curtilages when discussing permissible alterations and new developments.