It measures roughly eight metres across, and it has been sitting quietly under the fields while the world around it changed, largely unnoticed.

A ring-ditch, for those unfamiliar with the term, is a circular or near-circular ditch, often interpreted as the surviving trace of a burial mound or barrow whose central earthwork has long since been levelled by centuries of ploughing or weathering. What remains is the negative space, the cut, rather than any upstanding structure. The one at Ballymastone came to light not through accidental discovery but through planned investigation tied to local development pressures. A geophysical survey, carried out under licence number 05R012, identified the anomaly in the ground. This was followed by a test excavation, licensed as 07E0650, commissioned to inform the Donabate Local Area Plan, the kind of preparatory archaeological work that tends to happen when an area is earmarked for future development. The results, referenced in a 2007 report by Frazer, confirmed the presence of a possible ring-ditch approximately eight metres in diameter, though the word "possible" is doing some work here. The feature was identified but not fully characterised, which means its date, function, and condition remain open questions.

Because this site was investigated primarily as part of a planning process rather than a public heritage project, there is no marked trail, no interpretive signage, and no formal access point. The Ballymastone area sits in the broader Donabate peninsula, a part of north County Dublin where fingers of development and older agricultural land exist in close proximity. Visitors with a genuine interest in the site would do well to consult the National Monuments Service records before making the trip, as the precise location is not widely publicised and the feature itself is subsurface, invisible from the surface without equipment. What the landscape around Donabate does offer, for those already in the area, is a sense of how much archaeology can lie just out of sight beneath apparently ordinary ground, known only through the records of surveys carried out for reasons that had nothing to do with curiosity.