It has never appeared on any edition of the Ordnance Survey six-inch map, the standard tool by which generations of surveyors documented the Irish landscape, and yet it is unmistakably there, roughly fifteen metres across, revealed only when seen from above.

The site came to light through aerial photography, specifically Ordnance Survey photograph 2432, in which a circular cropmark or soil mark resolves itself into what appears to be an enclosure. Enclosures of this kind are among the most common archaeological features in the Irish countryside, typically the remains of a ringfort or ráth, a type of enclosed farmstead built and occupied roughly between the early medieval period and the Norman arrival. They were usually defined by an earthen bank and ditch, and served as a defended homestead for a farming family. At Bartoose, whatever once defined this circle has been so thoroughly absorbed into improved agricultural land that it leaves no trace a person walking the field could detect. The ground gives nothing away. Only the altered soil chemistry or differential crop growth, the things an aerial camera can read and a boot cannot, preserves its outline.