In a field in Broadfield, County Kildare, there is a site that cannot be seen by standing in it. It only becomes legible from the air, where a near-perfect circle roughly fifteen metres across emerges from the surrounding farmland as a cropmark, a ghostly impression left by buried archaeology that causes crops above it to grow differently from those around them. The differential, usually a matter of soil moisture and compaction over a filled-in ditch or disturbed ground, is invisible at ground level but resolves into a clear, coherent shape when viewed from above.

The enclosure at Broadfield came to attention not through excavation or fieldwork but through a screenshot. Aerial photography captured on Google Earth on 28 June 2018 recorded the mark during a period when conditions were right for it to show, and the image was subsequently noted and recorded. Circular enclosures of this kind are a familiar feature of the Irish landscape, ranging from the remains of ringforts, the most common upstanding monument type in Ireland, to earlier prehistoric enclosures whose original purpose remains harder to define. At fifteen metres in diameter this example sits at the smaller end of the scale, comparable in footprint to a modest ringfort, though without excavation it is impossible to say what lies beneath or when it was constructed.