The one under consideration here is an oval spread of burnt and heat-shattered stone measuring approximately 23 metres north to south and nearly 16 metres east to west. These mounds, known in Irish as fulachtaí fia, are among the most common prehistoric monuments in the Irish landscape. They are the accumulated debris of repeated cooking: stones were heated in a fire, dropped into a water-filled trough to bring it to the boil, then discarded once they cracked. Over time, the broken, blackened stone built up into the low, often horseshoe-shaped mounds visible today.

The proximity of the four sites at Knockagolig is what makes this particular location worth pausing over. A second fulacht fia sits just 11 metres to the east, a third roughly 60 metres to the south-southwest, and a fourth about 120 metres further in the same direction. Whether they were used simultaneously or accumulated across generations is not something the physical remains alone can answer. A note made by Bowman in 1934 may have recorded all four together, suggesting at least some of them were visible and identifiable as a group nearly a century ago, well before any formal archaeological survey of the area.