These curious features, known in Irish as fulacht fiadh, are essentially the accumulated debris of repeated heating: fire-cracked stones, discarded after being used to boil water in timber or stone troughs, piled up over generations into horseshoe-shaped mounds. They are extraordinarily common, yet their precise purpose remains genuinely contested, with theories ranging from communal cooking to brewing to bathing.

The example at Cranagh, in County Wicklow, dates to the early Bronze Age, placing its origins somewhere in the broad span between roughly 2500 and 1500 BC. It came to light not through dedicated fieldwork but as part of the infrastructural upheaval of the N11 road improvement scheme, when construction groundwork exposed what lay beneath the surface. Archaeologist Ellen O'Carroll led the excavation, which was assigned the site reference E3217. Road schemes of this kind have, perhaps unexpectedly, produced some of the most significant prehistoric discoveries in Ireland over the past few decades, simply because they cut long linear corridors through landscapes that had never previously been examined at ground level.