What sets it apart is both its nature and its company: this is one of several fulachtaí fia arranged in a loose line along the same watercourse, with closely related examples lying 25 metres to the south-east and another 50 metres to the north.

Fulachtaí fia, the Irish term for burnt mounds, are among the most widespread prehistoric monument types in Ireland. They typically consist of mounds of fire-cracked stone and charcoal-rich soil, the accumulated waste of a process in which stones were heated and then dropped into water-filled troughs to bring the water to a boil. The purpose remains debated, with cooking, textile preparation, and bathing all proposed by archaeologists over the years. The Killeen example came to light in 1996, when land reclamation works in the field exposed a surface spread of burnt material roughly four metres in diameter on the riverbank. The proximity of running water was essential to the process, and the linear clustering of several such sites along the Fiddaunglass suggests that this stretch of stream was returned to repeatedly, perhaps over a considerable span of prehistoric time. Heaps of later field clearance material lying about twelve metres to the east complicated the picture somewhat, raising the question of whether some of what survives is prehistoric deposit or later disturbance, which is why the site carries the cautious designation of a possible burnt mound.