The dunes of the Simpson run southeast to northwest, raked into long parallel ridges by the prevailing winds over tens of thousands of years. There are more than eleven hundred of them. Some stretch unbroken for as much as 200 kilometres. The most famous, known to travellers as Big Red and traditionally as Nappanerica, rises around 40 metres from the swale below - the great gateway dune near the desert's eastern edge that four-wheel-drivers gun their engines to climb. Between the ridges lie claypans, gibber flats and the dry traces of channels that flood only in the rarest years. The South Australian portion was first protected in 1985 as the Simpson Desert Regional Reserve, renamed Munga-Thirri–Simpson Desert Regional Reserve in 2018 to honour the country's traditional name.

For a long time outsiders believed the Simpson was simply uninhabitable - too dry, too vast, too hostile for anyone to live in its interior. They were wrong. The Wangkangurru lived deep within these dunes, sustained by mikiri: narrow native wells dug down through the sand, some as deep as seven metres, each capable of supporting a family group of dozens. The wells were the fixed points of desert life, and the routes between them were carried in song, so that a person could travel from water to water across hundreds of kilometres of identical-looking ridges. When the wells failed in a severe drought around 1900, the families walked out to the desert's edge. But the knowledge endured, and Wangkangurru descendants have since returned to relocate the old wells their ancestors knew.

The English name carries a smaller, stranger story. "Simpson" was bestowed in 1939 by the explorer Cecil Madigan, who led the first scientific crossing of the desert by camel - and who named it not for any feature of the land but for Alfred Allen Simpson, the Adelaide manufacturer and geographical society president who had helped pay for the expedition. So for decades the oldest sandhill country on the continent bore the name of a man who never had to cross it. Restoring Munga-Thirri to the map was a way of putting the deeper, truer name back where it belonged - a name given by the people who knew every dune in it.

The regional reserve no longer exists as a separate thing - and that is good news. In November 2021 the South Australian government combined the reserve with the neighbouring conservation park and reclassified the whole into the Munga-Thirri–Simpson Desert National Park: roughly 3.6 million hectares, or about 8.9 million acres. At a stroke it became the largest national park in Australia - bigger than Kakadu, and equivalent in area to four Yellowstones. Across the Queensland border it abuts a second Munga-Thirri park, so the protected dune-fields now run continuously across state lines. It is a desert that seems empty and is anything but - alive with desert birds after rain, threaded with ancient songlines, and now safeguarded at a scale to match its own.