The example at Ballaghadigue in north Kerry sits as a low oval mound, barely two-thirds of a metre above the surrounding ground, its modest profile giving little away. A small stream runs to its south-west, which is exactly where you would expect it: these structures, dating broadly to the Bronze Age, are almost always found near water, and for good reason.

A fulacht fia, in its simplest form, is a cooking site. The standard interpretation holds that stones were heated in a fire, then dropped into a water-filled trough to bring it to the boil, with the cracked and shattered stones discarded in a horseshoe-shaped mound around the trough. The mound at Ballaghadigue fits this pattern well. It measures roughly 14.2 metres west-north-east to east-south-east and 12 metres in the perpendicular direction, and in its southern sector there is a semicircular depression, about 3.2 metres at its widest, which likely marks the location of that original trough. A small quantity of burnt stones remains visible at the surface, the fractured and fire-reddened debris that is the defining signature of these sites. The proximity of the stream would have made the whole operation practical, providing the water supply that the process depended upon.