That density alone makes Ballycoskery unusual. A fulacht fia, for those unfamiliar with the term, is a prehistoric cooking site, typically a horseshoe-shaped or rounded mound of fire-cracked stones and charcoal left behind after repeated episodes of heating water in a nearby trough. They are among the most common archaeological monument types in Ireland, spread across boggy, waterside ground in their thousands, and yet the precise social rituals that generated them remain genuinely uncertain. Ballycoskery's cluster of four suggests either a site of repeated, intensive use over time, or a place where several working groups were operating in close proximity.

The principal mound sits in pasture about fifty metres south of a stream, a typical location given that fulachta fiadh relied on a ready water supply. It is roughly circular, measuring about twelve and a half metres north to south and just under twelve metres east to west, and rises only about forty centimetres above the surrounding ground. That low profile is partly a product of age and partly the result of more recent intervention: local information records that the mound was partially levelled around 1971. A second fulacht fiadh lies just one metre to the east, close enough that the two mounds may once have appeared to merge. A third is roughly forty metres to the east-southeast, and a fourth approximately eighty metres to the southeast, each one a separate accumulation of the same dark, fire-altered debris.