These are prehistoric cooking sites, typically Bronze Age in date, where stones were heated in fire and dropped into a water-filled trough to bring it to the boil. The characteristic result is a horseshoe-shaped mound of shattered, fire-cracked stone, dark with charcoal. What makes the Derryleigh example quietly striking is how thoroughly the land had swallowed it: according to local accounts, it lay buried beneath a layer of peat before anyone knew it was there.

It came to light around 1990, not through any planned investigation but during the routine digging of a land drain. The drain cut through the deposit, exposing burnt material resting on peat in the section wall, and in doing so both revealed and partially destroyed what had survived. That kind of accidental discovery is not unusual for fulachtaí fia, many of which formed in low-lying, marshy ground where peat subsequently accumulated over them. At Derryleigh, the burnt material does not sit in isolation. A stony layer runs northward from the site for some twenty metres, possibly the trace of an associated pathway, and two further spreads of burnt material lie about eight metres to the north, suggesting this was an area of repeated or related activity rather than a single isolated episode.