It measures around twenty metres long, just under twenty metres wide, and barely thirty centimetres high, a gentle swelling in the grass composed almost entirely of burnt material. That modest heap is, in fact, the remains of a fulacht fia, one of the most common yet persistently enigmatic monument types in the Irish archaeological record.

Fulachtaí fia are found in their thousands across Ireland, dating mostly to the Bronze Age, roughly 2000 to 500 BC. They are typically interpreted as cooking sites, though debate about their function has never fully settled. The usual reconstruction involves a trough filled with water, into which stones were heated in a fire and then dropped to bring the water to a boil. Over repeated use, those stones cracked and shattered, becoming useless for further heating, and were discarded into a mound nearby. That accumulated dump of fire-cracked, heat-blackened stone is what survives at sites like this one, a kind of slow-motion record of hundreds or even thousands of meals, or, as some researchers have proposed, episodes of bathing, textile processing, or other communal activity. The crescent or horseshoe shape common to many fulachtaí fia reflects the way spoil was piled around three sides of the working trough, though the example at Knockastuckane is described as roughly oval rather than the classic horseshoe form.