At Ballyoulster in County Kildare, something circular lies beneath a field, invisible to anyone walking across it, yet legible from the sky. A cropmark, roughly twenty metres in diameter, appeared in aerial imagery captured in May 2017, tracing the outline of an enclosure that left no obvious surface trace. Cropmarks form when buried features, such as ditches or walls, affect the way crops or grass grow above them. Soil disturbed by an ancient ditch tends to retain more moisture, encouraging lusher, taller growth, while compacted foundations can have the opposite effect. From ground level, nothing seems out of the ordinary. From above, the difference in vegetation draws a shape that might otherwise remain unknown for centuries more.

The enclosure itself has not been excavated or formally dated, and its function remains unconfirmed. Circular enclosures of this scale are common across Ireland and can represent a wide range of things, from prehistoric burial sites to early medieval ringforts, which were the enclosed farmsteads of rural Ireland between roughly the fifth and twelfth centuries. At approximately twenty metres across, this one sits at the smaller end of the spectrum, though size alone tells little without further investigation. Its existence came to wider attention when Colin Flynn noticed it in Google Earth imagery and shared the detail, leading to the site being recorded in 2020.