The site at Earlsrath is modest in scale, two small circular pits each roughly forty centimetres across, cut one after the other into the same ground, suggesting this was a place returned to, worked, and reworked over time rather than used once and abandoned.

The site came to light in 2007 during excavations carried out ahead of improvements to the N9/N10 road between Kilcullen and Waterford, the kind of infrastructure project that has, over recent decades, done as much for Irish archaeology as any dedicated research programme. The two furnaces were sequential, the second cutting through the eastern edge of the first, both sharing the same circular form with steep sides and a rounded base. The later pit retained an oxidised, heat-reddened lining, with black silty charcoal and slag, the glassy or stony byproduct of metalworking, still present inside. Attached to this second furnace was a slightly larger subrectangular working hollow, roughly a metre by 1.2 metres, presumably the space where a smith crouched or knelt to tend the fire and work the metal. Charred barley grains recovered from the charcoal were radiocarbon dated to between approximately AD 429 and 562, placing the activity firmly in the early medieval period. Twenty-seven metres to the north-east, a separate pit containing metalworking waste pointed to broader industrial activity in the vicinity. Four fulachta fia, burnt mound sites associated with the heating of water and found widely across Ireland from the Bronze Age onward, were also excavated in the same area, suggesting this hollow had been a place of organised activity across a very long span of time.