A prehistoric burial mound at Ballyallinan survives not as a visible earthwork but as a cropmark, a faint circular signature that only becomes legible from the air, when differential growth in the vegetation above betrays the buried archaeology beneath.

The monument was identified through aerial imagery rather than fieldwork. A Digital Globe orthophoto taken between 2011 and 2013 revealed a roughly circular area of approximately seventeen metres in diameter, defined by a scarp and an external ditch. A further Google Earth image captured on 8 April 2015 confirmed the cropmark clearly. Cropmarks of this kind form when buried features such as ditches retain more moisture than the surrounding soil, causing the plants directly above them to grow slightly taller or greener, while compacted material like a bank or a buried wall has the opposite effect, stressing the vegetation above it. From ground level the difference is invisible; from altitude it can read almost like a diagram. The record was compiled by Caimin O'Brien and uploaded in May 2020. A post-1700 field boundary runs roughly north-north-east to south-south-west across the north-western quadrant of the monument, meaning that at some point in the last few centuries a farmer drew a line across it without, perhaps, realising what lay underneath.

There is no visitor infrastructure here, and the monument is not signposted. The site sits within agricultural land, so access would require landowner permission. The cropmark itself is not visible at ground level, and even someone standing directly above the buried ditch would see only ordinary pasture. The most useful way to appreciate the site is through the freely available Google Earth archive, where the April 2015 image captures the circular outline with reasonable clarity. For those with an interest in how archaeology is recorded in Ireland today, Ballyallinan is a useful illustration of how much of the country's prehistoric landscape remains technically present but perceptible only through the right lens, at the right time of year, from several hundred metres above the ground.