In 1972, an aerial photograph, catalogued as FSI 592/1, captured a roughly circular cropmark about sixteen metres in diameter. That image remains the sole record of this site's existence. Standing in the field today, there is nothing whatsoever to see.

Cropmarks of this kind appear when buried features, such as the filled-in ditches that once defined a circular enclosure, affect how crops grow above them. Ditches that have silted up over centuries tend to retain more moisture than the surrounding soil, producing a slightly lusher, darker line of growth that, from altitude, traces the shape of the original earthwork. Circular enclosures of this general scale are a familiar feature of the Irish archaeological record, often associated with early medieval settlement, though without excavation it is impossible to assign a confident date or function to the site at Brownscross. The record was compiled by archaeologist Geraldine Stout and uploaded in August 2011, placing it formally within the national Sites and Monuments Record.

There is no practical way to visit this site in the conventional sense. The enclosure is not visible at ground level, there is no marker, and no feature distinguishes the field from any other stretch of cultivated land in north County Dublin. The stream to the west of the site has dried up, removing even that modest landmark from the landscape. What makes Brownscross worth knowing about is precisely this quality of near-total absence: a site that exists, documented and real, in a single black-and-white aerial photograph taken over fifty years ago, and nowhere else.