These are the remains of prehistoric cooking sites, typically identifiable as a horseshoe-shaped or kidney-shaped mound of burnt and fire-cracked stone, usually positioned close to a source of water. The working theory, supported by experimental archaeology, is that water was heated in a trough by dropping stones that had been fired in a hearth, reaching temperatures sufficient to boil meat. They appear in their thousands across Ireland, dating mostly from the Bronze Age, and yet the site at Portnahully represents one of the many that remain formally undocumented in any detail available to the public.

The location name itself offers some small context. Portnahully derives from the Irish, likely referencing a landing place or river access point, which fits neatly with what we know about how fulachtaí fia were typically sited. Water was not incidental to their function but central to it, and the low-lying ground near rivers or streams in Kilkenny's river-threaded south provided ideal conditions. Beyond the monument type and its general Bronze Age context, the specific history of this particular site, its dimensions, its condition, and any associated finds, remains inaccessible through published sources at present.

For anyone passing through this part of Kilkenny, knowing that such a site exists in the townland is itself a quiet provocation to look more carefully at the landscape. Fulachtaí fia are easy to overlook, often appearing as nothing more than a low grassy mound in a field, sometimes tree-covered or partially collapsed. The burnt stone that gives them away has a distinctive dark, friable quality, quite different from field clearance cairns or natural glacial deposits.