The furnace itself was modest, a bowl-shaped feature just 0.6 metres in diameter, containing around 50 grammes of iron slag. Beside it lay a dense spread of charcoal and ash, the residue of metalworking activity that had once taken place in what was, at the time, an ordinary rear garden in a medieval Irish town.

The story of how that garden came to exist is, in some ways, as remarkable as what was found in it. The site sits on the flood-plain of the River Nore, and the excavations, led by archaeologist Cóilín Ó Drisceoil, revealed a sequence of deliberate land reclamation efforts, successive deposits laid down to raise the waterlogged ground to a usable level. This kind of reclamation was common in expanding medieval towns, where pressure on space pushed development onto marginal, boggy ground along river margins. The work was probably completed by the 13th century, after which the reclaimed plot was put to practical use. Among the earliest deposits from the reclamation layers, excavators also recovered the partial remains of an infant skull, a quiet and sobering detail that speaks to the complexity of what urban ground holds.

By the late 18th or early 19th century, the site had been built over entirely, subsumed beneath the houses and shops that still define that stretch of Kilkenny's streetscape. The furnace and its associated deposits survived only because they lay beneath the level of the later cellars, sealed by everything that came after.