The site is a ring-ditch, a type of monument typically formed by a circular or near-circular trench dug in prehistory, often surrounding a burial mound that has long since been ploughed flat. What makes this particular example quietly interesting is not its visibility, which is essentially nil at ground level, but what a geophysical survey revealed lurking beneath the surface.

The survey was carried out under Licence no. 13R083 by the Discovery Programme, the Irish research body dedicated to archaeological investigation, as part of their 'Late Iron Age and "Roman" Ireland' project, an initiative examining Irish sites and material from roughly the last few centuries before and after the beginning of the Common Era. The results, published by Dowling in 2015, identified a penannular ring of approximately eight metres in diameter. Penannular simply means almost circular, a ring with a small break or gap rather than a fully closed circuit. Sitting just to the southeast of a previously recorded ring-ditch (catalogued as DU004-071002-), the newly surveyed feature also showed a single pit-type anomaly within its interior. That internal pit is of particular interest; it may represent the remains of a burial, a post, or some other deposit placed deliberately at the centre of the enclosure, though the survey alone cannot determine which.

The site is not marked, fenced, or signposted, and there is nothing for a visitor to see without the benefit of specialist equipment. Its value lies almost entirely in what the survey data tells researchers about the density of Late Iron Age activity in this part of County Dublin, where ring-ditches of this period are not uncommon but are rarely examined in such systematic detail. Anyone with an interest in the archaeology of the region would do better to seek out the Discovery Programme's published findings and the associated site record than to make a specific journey to Mallahow itself, where the landscape keeps its secrets thoroughly.