There is something almost absurd about a border this neat. The colonial draughtsmen who fixed the boundary did not care about the land it crossed; they simply chose a meridian and committed it to paper. The result is a frontier that ignores everything - dunes, plain, cliff, and ocean alike - and runs arrow-straight from the Bight to the Timor Sea. At Wilson Bluff the abstraction becomes concrete. Stand here and one foot can rest in the west while the other waits in the south, the two states divided by nothing you can see, only by an idea agreed on long ago and far away. The bluff was first recorded in 1885 as Wilson Point, then appeared as Wilson Bluff in the Australian Pilot, the mariner's guide, in its 1914 edition.

Names out here often arrive sideways, carried by whoever happened to be passing. This one came from E. A. Delisser, a surveyor working for a pastoral company, who is said to have named the headland after a "Professor Wilson of Victoria." An old photograph from 1903 places it near sandhills then called "Muddie Yarrah." But the land had older words attached to it long before any of these. In South Australia the bluff is also known as Yirgila - a reminder that the coast was named, walked, and known by Aboriginal people for thousands of years before a colonial surveyor reached for a professor's surname and pinned it to the cliff.

What makes the bluff worth the journey is the rock itself. These pale, crumbling walls are the southern lip of the Nullarbor - a single vast slab of limestone laid down when this whole region lay beneath a shallow sea. Geologists named the oldest and deepest layer after this very place: the Wilson Bluff Limestone, a soft, chalky stone packed with the skeletons of bryozoans, the lacy colonial animals that carpeted that ancient seabed in the middle to late Eocene, roughly 40 million years ago. The unit runs hundreds of metres thick. To look at the cliff face is to read a cross-section of deep time, each band a chapter of slow accumulation, now standing vertically where the land simply ends and drops into the swell.

From the clifftop the Great Australian Bight opens out in a single uninterrupted sweep of blue, with nothing between the rock and Antarctica but open water. East of here the same cliffs continue as the Bunda Cliffs, a near-unbroken rampart that runs some two hundred kilometres along the coast. There is no beach below, no gentle shelving - just a sheer white drop and the constant percussion of the Southern Ocean working at the limestone's base. Southern right whales come here in winter to calve in the sheltered water further along the coast, and the wind almost never stops. It is a place that feels less like a destination than a boundary in every sense: between two states, between land and sea, between the present and a seafloor 40 million years gone.