Burnt mounds, sometimes called fulachta fiadh, are among the most common archaeological features in Ireland: low, kidney-shaped heaps of heat-shattered rock and charcoal that accumulated wherever people repeatedly heated stones in a hearth and plunged them into water-filled troughs. They date mainly to the Bronze Age, though their precise function remains debated, with cooking, bathing, brewing, and craft work all proposed over the years. What made the Tullahedy example, designated Site A, worth closer attention was the complexity concealed inside that familiar shape.

The mound came to light during topsoil stripping for the bypass road, alongside two others in the same area. It measured roughly 19 metres north to south and 23.5 metres east to west, standing to a depth of about 0.7 metres, and three-quarters of it was excavated, with the remainder left in place. Beneath the succession of burnt clay and stone layers that formed the mound itself, archaeologists uncovered seven clay-lined troughs, areas of cobbled surface, and evidence of post and stake structures. One trough was particularly carefully built, with a post set at each corner and a cobbled surround. The north-eastern corner of the site was notably different from the rest: it preserved two distinct clay surfaces, and the upper of these produced worked chert, worked flint, and a perforated stone bead. That bead closely resembled examples recovered from a Neolithic site also at Tullahedy, suggesting activity in this area stretching back well before the Bronze Age mound was built up over it. The lower clay layer yielded what may be two microliths, small worked flint blades associated with Mesolithic and early Neolithic peoples. Later in the mound's sequence, deposits of fine yellow sand appeared alongside a concentration of small iron objects mixed with burnt animal bones, and when the site was finally abandoned, substantial quantities of iron slag were left across its surface, pointing to metalworking in its final phase of use.