At Killawillin in County Cork, one such site sits quietly in pasture on a south-facing slope, marked by little more than a spread of burnt material lying close to a stream. That proximity to water is no accident. It is, in fact, the whole point.

A fulacht fia, the term used in medieval Irish sources, is generally understood as a burnt mound, the accumulated debris of a cooking or heating method that involved placing fire-cracked stones into a water-filled trough until the water boiled. The stones, unable to withstand repeated heating and quenching, shatter and blacken, and over time the discarded fragments build up into the low, horseshoe-shaped mounds that characterise these sites. They date most commonly to the Bronze Age, roughly 1500 to 500 BC, though some have produced earlier or later dates. The Killawillin example follows the classic pattern: a source of running water nearby, a gentle slope to aid drainage, and the telltale dark spread of heat-shattered stone working its way into the soil. Whether the sites were used primarily for cooking, bathing, textile processing, or some combination of these remains debated among researchers, and Killawillin offers no particular evidence to settle the question one way or another. What it does offer is a quiet, legible trace of repeated, organised activity carried out in this particular corner of Cork across a span of time that dwarfs anything built since.