The one at Faheens in County Mayo is a quiet example of a type that still generates genuine archaeological debate. The typical form is a horseshoe-shaped mound of burnt and cracked stone, dark and waterlogged, sitting low in a field or beside a stream. They date mostly to the Bronze Age, roughly 1500 to 500 BC, and the leading theory holds that they were outdoor cooking sites. Water was collected in a trough, often timber-lined, and stones were heated in a nearby fire before being dropped into the water to bring it to the boil. The process is surprisingly efficient, and experimental archaeologists have demonstrated that a substantial joint of meat can be cooked this way in a few hours.

The burnt mounds that survive are essentially the accumulated waste of repeated use, the discarded cracked stones piling up over many seasons or even generations of activity. Some researchers have proposed alternative uses, including sweat houses, textile processing, or brewing, and it is possible that a single site served several purposes over its lifetime. Mayo has a notable concentration of these monuments, which is partly a reflection of the county's boggy, wet terrain, the kind of low-lying ground near water sources where fulachtaí fia are most commonly found. The Faheens site sits within this broader pattern, a small but genuine trace of Bronze Age activity in the landscape.