In a large arable field in Collinstown, north County Dublin, an ancient enclosure lies invisible for most of the year, buried beneath crops and soil, revealing itself only as a faint discolouration in the vegetation when seen from above at the right moment. It surfaces not to the eye of a walker, but to the lens of a satellite.

The feature is a ring-ditch, a sub-circular enclosure roughly eleven metres in external diameter, identified on Digital Globe satellite imagery on 24th July 2018 by Christine Baker. Ring-ditches are typically the eroded remnants of prehistoric burial monuments, most often round barrows or cairns whose earthen mounds have been ploughed flat over centuries, leaving only the encircling ditch as a ghostly trace in the subsoil. What Baker spotted was a crop-mark, the phenomenon by which buried ditches or pits, retaining more moisture than the surrounding ground, cause the plants growing above them to ripen at a slightly different rate, producing a visible pattern from altitude that is undetectable at ground level. The site sits on the south-facing slopes of a broad east-west ridge, with extensive views east towards the Irish Sea and south towards the Dublin mountains, a position that would have carried considerable significance for whoever constructed the original monument. The record was compiled by Margaret Keane and uploaded just two days after the discovery, on 26th July 2018.

The enclosure lies in the north-east corner of a large arable field, approximately forty metres west of the road running between Lusk and Skerries. There is nothing to see on the ground; the archaeology here is entirely subsurface, and the field is privately farmed land. The crop-mark itself would only be visible from aerial or satellite vantage points, and only during the narrow seasonal window when crop stress makes the buried features legible. For anyone travelling the Lusk to Skerries road, the site is simply a field edge, the ridge carrying the eye outward across the coastal plain rather than downward into what lies beneath it.