It is not obviously dramatic from a distance, but the details reward attention: the mound measures roughly fourteen metres north to south and twelve east to west, and where the thin sod cover has eroded away, dense black, charcoal-rich soil packed with small limestone fragments is exposed. At the western end of the central depression, a kerb of low, close-set upright stones still protrudes a quarter of a metre above the turf, defining the curved inner edge of what was once a working trough.

This is a fulacht fia, a type of prehistoric cooking site found across Ireland in the thousands. The typical method involved heating stones in a fire, dropping them into a water-filled trough to bring it to the boil, and using that heated water to cook meat. The burnt and shattered stones were then discarded, accumulating over time into the characteristic horseshoe or kidney-shaped mounds that survive today. At Aghawinnaun, the trough's U-shaped depression opens eastward, directly towards a spring that issues from the base of the low rock face backing the terrace. The spring is still in use as a water source, with large boulders piled around it by more recent hands, a detail that speaks to the enduring logic of the location. The mound's orientation is not accidental; the trough was positioned precisely to draw on that supply. A second fulacht fia lies approximately 700 metres to the south and is visible from the site, suggesting this stretch of hillside saw repeated, possibly sustained, prehistoric activity rather than a single isolated episode of use.