It measures roughly eight metres by eight metres and rises only about half a metre from the ground, the kind of feature that could be mistaken for a natural hummock or a drainage spoil heap. It is, in fact, a burnt mound, one of the most common yet least-understood monument types in the Irish archaeological landscape.

Burnt mounds are the accumulated debris of a Bronze Age process that involved heating stones in a fire and dropping them into a water-filled trough to bring the water to a boil. The shattered, heat-stressed stones were then discarded in a pile nearby, which over centuries became the crescent or kidney-shaped mounds now found across Ireland and Britain. Archaeologists sometimes refer to them by the Irish term fulacht fiadh, meaning roughly a cooking pit of the wild, though their precise function remains debated: some researchers favour communal cooking, others suggest bathing, textile processing, or even brewing. What they consistently produce is exactly what survives at Ballydineen, a compact heap of fire-cracked stone mixed with the blackened soil that comes from prolonged, repeated burning. The site has not escaped entirely intact; a forest drain has cut partially into the mound, exposing something of its interior profile.