Roughly eleven metres in diameter, the feature exists not as a visible mound or earthwork but as a cropmark, the faint differential in how crops grow over buried soil disturbances, which from the air resolves into a clear circular outline. This is how a great many ancient funerary and enclosure sites are now first identified across the Irish midlands, where centuries of agriculture have flattened the physical evidence but left the underlying archaeology intact beneath the soil.

The cropmark was identified on aerial imagery captured in January 2020, when low vegetation or bare ground conditions made the circular form legible in satellite photographs. Circular enclosures of this kind are frequently associated with prehistoric burial activity, and the term barrow refers broadly to a mound or enclosed area raised over or around a burial; in Irish archaeology the category includes ring-barrows, which typically survive as low earthen rings rather than prominent mounds. At roughly eleven metres across, the Knock Killua feature sits within the range of smaller ring-barrow monuments known elsewhere in the midlands. Its presence here, discernible only from altitude, is a reminder of how much of the Irish archaeological landscape remains legible only in this indirect way, read through the behaviour of grass and grain rather than stone or earthwork.