One of them is a fulacht fia, the term used for a type of prehistoric cooking site, typically identified by a mound of heat-shattered stones and charcoal left behind after repeated cycles of heating stones and dropping them into water-filled troughs. The example at Ballyhogan was recorded as a spread of charcoal and broken stones measuring roughly six metres by five, but it leaves no trace above ground level.

The fulacht fia came to light almost incidentally, discovered during an investigation prompted by something else entirely. In June 1954, land reclamation works carried out under the Land Rehabilitation Project disturbed a naturally raised area of approximately twenty metres in diameter in the same field, a feature that had locally been identified as a fort. When the bulldozing began, human remains emerged. Breandán Ó Ríordáin of the National Museum carried out an investigation and found bones representing several individuals scattered across the surface, along with small stones, but no evidence of formal grave structures. The only artefact recovered was a large, square-headed iron nail that appeared to adhere to a fragment of human bone. Local tradition identified the place as Kilwarig, and it was known in the area as a burial site for unbaptised children, though adult remains were present too. Such informal burial grounds, sometimes called cillíní, were used for those excluded from consecrated ground, and they are often found associated with older, pre-Christian landscape features. The fulacht fia was noted in the same field during that same investigation, its proximity to the burial ground apparently coincidental, the two sites belonging to entirely different periods and purposes.