The ground above them is under tillage, ploughed and worked like any other agricultural field, giving no hint that something old and significant is folded into the earth beneath. That invisibility is not merely a matter of overgrowth or neglect; these features simply cannot be seen at ground level at all, which places them in a quietly strange category of monument, known to archaeology but effectively absent from the landscape.

The three circular areas, defined by banks with an average diameter of around 6.25 metres, were first recorded in the 1950s by archaeologist P. J. Hartnett, who noted their position near the shoreline immediately south of the Bremore passage tomb cemetery. A passage tomb is a type of prehistoric burial monument in which a stone-lined corridor leads to a chamber, typically covered by a large mound; the Bremore cemetery is a recognised grouping of such monuments on the headland. Decades after Hartnett's observations, a geophysical survey carried out under licence in 2006, with results published by Gimson, managed to identify what may correspond to one of his three sites. That anomaly takes the form of a circular ditch roughly 25 metres in diameter, located approximately 110 metres south-west of the principal mound in the cemetery. No internal features were detected within it. The other two sites Hartnett described did not show up in the survey at all. The headland has seen further investigation over the years, including a constraint study by Margaret Gowen and Company Ltd. carried out ahead of a proposed port development, and fieldwalking and lithic analysis as part of an MA study by Collins in 2007.

Bremore headland sits on the Dublin coastline north of Balbriggan, and the passage tomb cemetery there is the more visible draw for anyone making the trip. The barrows themselves offer nothing to see on the surface, which makes a visit more of an act of imagination than observation. What the geophysical survey quietly confirms is that the area around the cemetery was a more complex and layered place in prehistory than its present agricultural surface suggests. Anyone interested in the broader site would do well to focus on the passage tombs themselves, using the known location of Mound I as a rough reference point for orienting themselves to where these underground anomalies are thought to lie.