It is, in fact, the remains of a fulacht fia, a type of prehistoric cooking or processing site found in considerable numbers across Ireland, particularly in low-lying or waterside locations. The characteristic material, known as burnt mound spread, consists of fire-cracked stones that were heated and then plunged into water-filled troughs to bring liquid to a boil, leaving behind a distinctive horseshoe-shaped or spread deposit that survives long after everything else has gone.

What makes the Garranes site quietly interesting is its immediate context. A second fulacht fia lies close by, suggesting this stretch of ground was returned to repeatedly, perhaps across generations. Nearby too is the site of a holy well, a category of place that in Ireland often marks a source of fresh water with long and layered significance, pre-Christian in origin but frequently absorbed into later religious practice. The stream that once flowed from that well has since dried up, which may explain something about how the landscape has shifted since these places were in use. Water access was essential to a fulacht fia, and the proximity of a reliable source would have made this a practical, even attractive, spot for repeated activity.