The one at Gleninagh in County Clare sits on a narrow terrace of a north-facing slope at the foot of Cappanawalla hill, barely five hundred metres from the shore, positioned just ten metres from a natural spring. That proximity to water is no coincidence. A fulacht fia is a burnt mound, typically Bronze Age in origin, consisting of the accumulated debris of fire-cracked stones used to heat water in a trough. The stones fracture when plunged from fire into water, and over time the discarded fragments build up into a characteristic horseshoe shape around the trough itself.

The Gleninagh example fits that classic form closely. The mound measures sixteen metres on its longer axis and nearly fourteen on its shorter, with a maximum height of 1.7 metres, making it a substantial survival. It opens to the west-south-west, and two large boulders at the south-west and west-south-west ends define the edges of the trough area, which spans roughly 5.8 metres by 5.3 metres. What the site was used for remains genuinely contested: cooking, textile processing, bathing, and brewing have all been proposed at various points by researchers, and excavated examples have produced evidence consistent with more than one of these activities. The site was recorded on Robison's map of 1977, confirming that it was already a recognised feature of the local landscape several decades ago.