What appears to be a modest rise in a field is in fact a fulacht fia, the burnt-mound remains of a cooking site used in prehistoric Ireland, typically by filling a trough with water and heating it rapidly using fire-cracked stones. Once the stones cooled and cracked, they were discarded at the edge of the trough, accumulating over repeated use into the characteristic horseshoe-shaped mound that survives today. At Ballyduane, the main mound measures roughly 11.5 metres north to south and 7.3 metres east to west, rising to a height of around 1.1 metres, with a shallow central depression of about 0.3 metres depth marking where the trough would have been. A smaller, elongated mound sits to the northwest, connected to the main mass by a narrow bank of the same burnt material, suggesting the site saw extended or repeated activity.

The townland was noted as holding two such features by Bowman in 1934, one on land belonging to a J. Reen, the other to an M. Quinn. The Ballyduane example recorded here is one of that pair, though which landholding it corresponds to is not entirely settled. Fulachta fiadh are among the most common prehistoric monuments in Ireland, numbering in the thousands across the country, yet individual sites like this one rarely attract much attention. They accumulate quietly in corners of fields, lumpy and heat-blackened, easy to overlook precisely because there are so many of them. The irregularity of this particular mound, and the secondary elongated deposit linked to it, give it a slightly more complex character than many.