Hand stencils are among the oldest and most universal forms of human art, found in caves on nearly every inhabited continent, and yet they never lose their power. At Murrawijinie, the ochre prints are a direct, intimate record of the people who used these caves: not a drawing of something else, but the literal outline of a living hand held against the stone. In the dry, sheltered dark, the red has held for an astonishing span of time. The marks tell us that people came here deliberately, into the cool of the earth, perhaps for shelter from the brutal heat of the open plain, perhaps for water, perhaps for reasons woven into ceremony and belief that belong to the traditional owners of this country. Among the makers, it is understood, were women and children, venturing down into the caves in the middle of what seems, on the surface, like nowhere at all.

Murrawijinie is really a group of caves, reached about 10 kilometres north of the Nullarbor Roadhouse along a rough track off the Eyre Highway. The way in is through a doline, a sinkhole where the limestone roof of an older cavern has collapsed and opened a window into the dark; two more entrances lie close by. This is the signature of Nullarbor country. The plain is the world's largest single exposure of limestone, and rainwater has spent millions of years dissolving it from within, riddling the rock with caves, sinkholes and blowholes that breathe with the changing pressure of the air. Above ground there may be nothing but saltbush to the horizon. Below ground is a hidden architecture of hollows, and the sinkholes are the doorways between the two worlds.

The caves are not silent. Hawks and swallows nest on the ledges and in the shadowed openings, wheeling up out of the sinkholes into the glare of the plain and dropping back down into the cool. For birds, the dolines offer shelter, shade and safety from the heat and the wind in a landscape that gives little of any of it. The same coolness that drew people underground draws the wildlife too. To descend even a few metres into a Nullarbor sinkhole is to feel the temperature fall and the light change, the open furnace of the plain giving way to a hush of stone and the soft sound of wings overhead.

Unlike the strictly protected caves elsewhere on the Nullarbor, Murrawijinie is open to the public, though it asks for caution. The track in is rough, the sinkholes are real drops, and the country is remote and unforgiving. Since June 2013 the cave has lain within the Nullarbor Wilderness Protection Area, which guards the surrounding landscape. What it cannot fully guard, anywhere, is the fragility of what the caves hold. The ochre hands on the wall are not a curiosity to be touched or traced; they are heritage, the work of the people who knew this land first and whose descendants carry that connection still. To stand before them, in the cool dark with the birds calling above, is to be a guest in a place that was sacred long before any road crossed the plain above it.