A fulacht fia is a type of prehistoric cooking or processing site, typically consisting of a trough, a hearth, and a mound of burnt and shattered stone accumulated over repeated use. The heat-fractured angular stones are the giveaway: rocks were heated in a fire, dropped into a water-filled trough to bring it to the boil, then discarded in a growing heap once they cracked and became useless. Over centuries, those heaps can survive as low, horseshoe-shaped mounds, common across Ireland but rarely dramatic to look at.

At Capnagower, the site has been badly disturbed, and what survives is essentially a lens of those characteristic small burnt stones exposed in the cut faces of the drain where it bifurcates. The visible deposit runs roughly three metres on a south-southwest to north-northeast axis and about two and a quarter metres across. Scatters of burnt stone are also visible on both banks of the drain, mixed among the many small boulders that the digging threw up. The surrounding land is enclosed grazing, and the slope looks out eastward over the point. Fulachta fia are frequently found near water sources, which were essential to their function, and the small shallow stream channelled by the drain here fits that pattern precisely. The site at Capnagower was documented as part of the New Survey of Clare Island, a project published by the Royal Irish Academy in 2007 under the editorship of Paul Gosling, Conleth Manning, and John Waddell, which brought systematic archaeological attention to an island more often discussed for its association with the sixteenth-century chieftain Gráinne Ní Mháille.