A cropmark enclosure of roughly thirty metres in diameter shows up on aerial imagery, its outline rendered by differences in how vegetation grows over disturbed or compacted soil beneath the surface. The circle is clear enough to photograph, but silent on what it actually is.

Cropmarks form when buried features, walls, ditches, or filled pits, influence moisture retention in the soil above them, causing the overlying crops or grasses to grow at slightly different rates. From ground level, nothing is visible. From altitude, the pattern can be striking. Circular enclosures of this kind in the Irish midlands are frequently associated with early medieval ringforts, the farmstead enclosures that once numbered in the tens of thousands across the island, though they can also represent prehistoric activity or later features. Without excavation, the Heathstown example cannot be assigned confidently to any period. The site came to wider notice through Google Earth aerial photographs taken in January 2020, with the feature identified and recorded shortly afterwards.