Recorded in the 1840s as Lissnaguan Fort, this earthwork sits in pasture with views south towards Killeen Mountain, and the tradition attached to it is blunt: a battle was fought here, and after the defeat of the Irish, the heads of their commanders were spiked on the fort. The name itself may carry an echo of that story, though the precise engagement it refers to has not been pinned down with certainty.

The structure is a rath, the Irish term for a roughly circular enclosure defined by an earthen bank or, in this case, a scarp, that raised bank of sloping earth which would originally have enclosed a farmstead or settlement, most likely in the early medieval period. This particular example measures about 36 metres north to south and 34 metres east to west. The scarp is not uniform: it rises from a modest 0.3 metres at the north-west to a height of 2.3 metres at the south before dropping away again to the south-west. A possible entrance, roughly 3 metres wide, opens at the north. Along the eastern arc, a slight lip about 2.5 metres wide and 0.1 metres high may be the last trace of a more substantial enclosing element, now largely lost. An overgrown field boundary running north to south, capped with trees, cuts across the south-west to north-west section of the circuit, and mechanical clearance on the flanks has caused intermittent damage between the north-east and south-east. In a few places, the underlying earth is exposed where the ground surface has been disturbed.

The interior, slightly uneven underfoot, remains in pasture, with a north-to-south hollow visible in the southern quadrant. The knoll's elevated position would have made it conspicuous in the landscape from the beginning, which may be precisely why, in whatever conflict the local tradition recalls, it became the site chosen to make an example of the defeated.