For generations, perhaps from around 1750, seafarers from Makassar in present-day Indonesia sailed each year on the north-west monsoon to the coast of Arnhem Land. They came for trepang - the sea cucumber, bêche-de-mer, prized in Chinese kitchens - which they gathered, boiled, and dried on these shores before carrying it home to trade. When the explorer Matthew Flinders met a Makassan fleet off the English Company Islands in 1803, their captain Pobassoo explained the whole seasonal trade to him. Unlike encounters elsewhere on the continent, the relationship between Yolngu and Makassan was largely one of exchange rather than conflict. Goods, words, and customs passed between them, and some Yolngu sailed away on the praus to Makassar and beyond, returning with knowledge of a wider world.

The trade ended in 1906, when the government restricted the licences that allowed the Makassan fleets to come. But the memory did not fade, because Yolngu had fixed it in the ground. Oral history records that a man named Yumbul made the first stone pictures, and that his second son, Dhatalamirri, was entrusted with the site and added more. The arrangements spread across roughly 80 by 70 metres in three groups, depicting Makassan praus and houses, the stone hearths where trepang was boiled, and Yolngu camps, canoes, and fish traps. Some images are simple outlines; others use stones of different sizes to give weight and detail. The makers knew these ships intimately - their knowledge could only have come from sailing aboard them.

In 1967 the researcher Campbell Macknight and Bill Gray of the Northern Territory Administration came to record the site, and two senior Yolngu men walked them through its meaning. Mungurrawuy Yunupingu, a Gumatj custodian - and a celebrated bark painter and father of future Yolngu leaders - and Mawalan Marika explained how the divisions within each stone vessel marked off its parts, and gave the Makassan names for the rudder, the bowsprit, the tripod mast and its rigging. Their account, published in 1969, showed that Yolngu had spent enough time aboard the praus to learn every working part. The custodians were clear about something else, too: Wurrwurrwuy held no sacred associations. It was, they said, a record of the past, kept so that younger men would understand the Makassan world their ancestors had known.

That ordinariness is exactly what makes Wurrwurrwuy extraordinary. Across Aboriginal Australia, arranged stones are almost always tied to ceremony and the sacred; here, uniquely, they document the everyday and the historical. The detailed cutaway views of the praus - showing how a ship was laid out inside - are rare in Aboriginal depictions of vessels in any form at all. Australia recognised the significance: the site was added to the Northern Territory Heritage Register in 2007 and the Australian National Heritage List in 2013, listed in part for its sheer rarity. Today it is fenced, signposted, and cared for by Dhimurru's Aboriginal rangers - a Yolngu archive of cross-cultural history, still tended by Yolngu hands.