On a south-west facing slope above the Nier valley in County Waterford, a low, scrub-covered mound sits close enough to a stream that its original purpose becomes legible once you know what to look for. Locals call it a lios, a word usually associated with a fairy fort or ringfort, but the structure is almost certainly something older and more functional: a fulacht fia, the remains of a prehistoric cooking place.

Fulachtaí fia are among the most common ancient monuments in Ireland, found in their thousands across the country, almost always near water. The working principle was straightforward: stones were heated in a fire, then dropped into a water-filled trough to bring it to boiling point, allowing meat to be cooked. The characteristic horseshoe or U-shaped mound that survives at a fulacht fia site is the accumulated debris of that process, the cracked and fire-shattered stones discarded after each use over many cycles of heating. At Knockanaffrin, that accumulation has built into a mound measuring roughly 16 metres east to west and just over nine metres north to south, reaching a maximum height of nearly two metres. The mound is open to the north, where a hollow depression, just under a metre below the surrounding ground level, marks what was likely the position of the trough. A stream runs about 60 metres to the south, close enough to have supplied the water the whole operation depended on. The southern slope of the mound still shows small fractured stones beneath its covering of soil, the characteristic signature of the process that formed it.