The one at Miles, in County Cork, is a quiet example of a feature that once would have been a busy, practical site. A fulacht fia typically appears today as a low, horseshoe-shaped mound of fire-cracked stone and dark, charred soil, the accumulated debris of repeated heating. The stones were placed in a fire, then dropped into a water-filled trough, usually timber-lined and sunk into the ground, to bring it to the boil rapidly. What exactly that boiling water was used for has kept archaeologists arguing for decades: cooking, textile processing, brewing, and bathing have all been seriously proposed.

The type belongs overwhelmingly to the Bronze Age, roughly 2000 to 500 BC, though some sites have earlier or later activity. They tend to cluster near water sources, since the trough needed constant replenishment, and County Cork has one of the densest concentrations in the country. The mound shape is a byproduct of the work itself: cracked and spent stones were simply tossed aside after each use, building up over time into the characteristic curved bank that survives to this day. That so many have endured at all owes something to the boggy, marginal ground they often occupy, land that was never worth the effort of ploughing flat.