But this kind of deposit, known in Irish archaeology as a fulacht fia, is one of the most commonly encountered prehistoric monuments on the island, and the one at Maglin, near Ballincollig, is a good example of how they tend to come to light: not through deliberate excavation, but by accident, when something else is being built.

The site was found in 2001 during test-trenching carried out ahead of construction work on the N22 Ballincollig Bypass. Underneath the scatter of heat-shattered stones, archaeologists uncovered an oval pit measuring roughly three metres by one and a half, and sunk to a maximum depth of sixty centimetres. This pit, bowl-shaped in profile, is interpreted as a probable trough, which is the functional heart of a fulacht fia. The standard theory holds that such sites were used for cooking, most likely by filling the trough with water and heating it by dropping fire-heated stones into it until the water boiled. Those stones, once cracked by repeated heating and cooling, were discarded to form the characteristic mound that survives above ground. Whether the sites were also used for bathing, textile working, or other purposes remains debated among specialists, but the basic technology is well understood. The Maglin trough, at just over half a metre deep, is a modest but recognisable example of the type.