But their shape gives them away. Arranged in a broad U that opens towards the water, they represent a fulacht fia, a type of prehistoric cooking site found across Ireland in enormous numbers, typically Bronze Age in date. The basic principle involved heating stones in a fire, dropping them into a water-filled trough to bring it to a boil, and using the resulting heat to cook meat. The spent, fire-cracked stones were then discarded in heaps, and it is those accumulations that survive as the horseshoe-shaped or crescent-shaped mounds we see today.

This particular example at Capnagower measures roughly 11.5 metres north-north-west to south-south-east and 12.2 metres east-north-east to west-south-west, rising to a maximum height of about one metre on the eastern side. The north-eastern arm is the more substantial of the two, and at its north-western end, towards the flat summit, some burnt stone is still visible at the surface. A small oval mound sits just beyond this arm, possibly a subsidiary dump of material from the same episodes of use, though no stone breaks through the turf there. The south-western arm is lower and less pronounced. Between the two arms, at the south-eastern end, there is a characteristic saddle-like depression that gradually fades as it meets the upslope edge of the site. What makes the location particularly striking is that another fulacht fia of broadly similar character lies just twenty metres to the north, also positioned along the same stream, suggesting this stretch of water was a focus for repeated activity over time. The proximity of the two sites to each other, and both to flowing water, is entirely consistent with how fulachtaí fia tend to cluster in landscapes across Ireland.