The kiln, a small semi-circular structure of vernacular stonework, was built into an earthen scarp at the south-western edge of a much older circular enclosure. That enclosure has long since been levelled, and the kiln itself is a ruin. But the combination of the two, one thing preserving the faint ghost of another, is what makes this particular patch of ground worth a second look.

The enclosure appears on the Ordnance Survey six-inch map of 1837, recorded as a circular earthwork roughly 25 metres in diameter. It does not appear on later editions, suggesting it had already been ploughed or otherwise removed from the landscape by the late nineteenth or early twentieth century. It was probably a rath, the Irish term for a ringfort, a class of enclosed farmstead built mostly in the early medieval period, typically defined by one or more earthen banks and ditches. At Ballydrum, almost nothing of that original form survives. What remains is a low, stony scarp, no more than 0.6 metres high and curving for about 8 metres in a shallow south-westerly arc. It endures only because a limekiln, a small stone furnace used to burn limestone into quicklime for agricultural use, was constructed against it at some later point. The weight and bulk of the kiln seem to have protected that particular section of bank from the same fate as the rest.

The surviving scarp is modest to the point of near-invisibility, and the limekiln itself is ruined. The interest here lies less in what you can see than in the layered accident of survival: a medieval enclosure preserved, in its last trace, by a piece of nineteenth-century farm infrastructure.