They appear as low, horseshoe-shaped mounds, typically found near water, and they mark the sites where Bronze Age people heated water by dropping fire-cracked stones into a trough. The burnt and shattered stones were raked out after use and piled to the sides, gradually building up the distinctive mound shape that survives to this day. What they were actually used for, cooking being the traditional explanation, has been debated by archaeologists for decades, with brewing, hide-working, and bathing all proposed as alternatives.

The example at Tullyvoghan in County Clare is one of many such sites recorded across the county. Clare has a particularly dense distribution of Bronze Age activity, and fulachtaí fia are a recurring feature of its low-lying, waterlogged ground, precisely the kind of terrain these sites favour. The townland name Tullyvoghan derives from the Irish, and like many Clare placenames it preserves a layer of landscape description older than any written record. The site itself fits a pattern repeated across Ireland from roughly 1500 BC onwards, a period when communities were leaving physical traces in the land at a rate that still surprises those who study it.