It is modest by any measure, barely twenty centimetres above the surrounding ground, yet it represents one of the most persistently mysterious categories of monument in the Irish landscape.

A fulacht fia is a Bronze Age cooking site, or at least that is the most widely accepted interpretation of a feature type found in its thousands across Ireland. The typical arrangement involves a timber-lined trough filled with water, heated by dropping fire-cracked stones into it until the water boiled; the spent, fragmented stones were then discarded to the sides, accumulating over repeated use into the characteristic horseshoe-shaped mound that survives today. The example at Kilcullen follows this form closely. The mound measures ten metres in length and seven metres in width, with the open end of the horseshoe, roughly two metres wide, facing south-west. It is precisely that gap which would have faced the working area, the trough and the fire, with the curved back of the mound built up from centuries of discarded burnt stone. The material underfoot is the archaeology itself, blackened and heat-shattered, preserved simply by being left where it fell.