Hallett Cove is one of South Australia’s foremost natural science treasures. Exposed examples for prime geological concepts of superposition of strata, depositional unconformities (representing time breaks), and folding and faulting of sedimentary rocks are clearly displayed. Professor Ralph Tate discovered evidence of ancient glaciation in the form of polished and striated rock surfaces on the clifftops in 1877 and the site has attracted scientific attention ever since. The area has seen at least three separate glaciations in its long history, and displays evidence of a cold, dry, windy climate during a fourth. Recognition of past climatic variations provides a historical context for understanding current climate change. Besides its geoscientific features, it is an important anthropological and botanical site. The proximity to Adelaide, the diversity of rock types and field relationships, the evidence of past glaciations, and the remnant native flora and fauna have made Hallett Cove a highly valued conservation park with wide application in public education. Despite publication of at least five field guides to Hallett Cove, no modern detailed geological map using current stratigraphic nomenclature has hitherto been published. Following frequent inquiries made lately about whether such maps of Hallett Cove do exist, the author drew upon personal observations gathered over many years to construct a new geological map of the conservation park. The present ready availability of fully rectified colour aerial imagery enabled photo-interpretation of lithological boundaries, and their interpolation between control points located by GPS. Cartography was carried out simultaneously with photo-interpretation, on screen, using GIS software. Symbols and colours for geological units were selected to approximate widely used colour schemes and lithological overprints. The map consists of a series of superimposed layers, each representing a separate geological unit and topographic features, and is presented as a layered PDF. These units are combined into folders of age-related layers within the PDF. Folders, as well as individual units, can be switched on or off. With all layers on, the map represents all geological units exposed at the surface, including soil cover, topographic features and grid-lines. By switching successive underlying layers (or folders) off, the various strata can be progressively stripped until the interpreted bedrock geology is laid bare.