A low earthen bank on a gently east-facing slope in Dooneen Upper, County Limerick, sits squarely in that category. What was once described as a semicircular enclosure roughly 30 metres in diameter had, by the time anyone returned to check, apparently vanished from the ground altogether, leaving only its faint impression on aerial imagery as evidence that it had ever been there.

The site came to light in 1995, when archaeologist Celie O'Rahilly of Limerick Corporation carried out an archaeological assessment ahead of a proposed racecourse development at Greenmount. O'Rahilly logged it as Site 21, describing a low bank defining a semicircular area that had been partially cut through by a cattle yard on its western side. Enclosures of this general type, which are among the most common monument forms in the Irish landscape, were used across a broad sweep of prehistory and the early medieval period for purposes ranging from settlement and stock management to ritual activity. Without excavation, the precise date and function of any individual example is rarely certain. When the Archaeological Survey of Ireland revisited the Dooneen Upper site in 2000, no enclosing element was visible on the ground. The picture became stranger still when later analysis showed the monument appearing on Ordnance Survey Ireland orthoimagery captured between 2005 and 2012, yet absent from Google Earth imagery of the same area, a discrepancy that says something about the limits of any single source when tracking low-profile earthworks.

The site lies in pasture approximately 20 metres northeast of the townland boundary with Logavinshire. Because the surviving earthwork, if any remains, is by nature subtle, a visitor expecting a dramatic feature will be disappointed. What is worth bringing is an awareness that even slight variations in ground level, particularly when seen in low winter light or after rain, can reveal the ghost of an old bank that registers as nothing more than a gentle shadow on the grass. The surrounding farmland is private, so any approach would require permission from the landowner. The Ordnance Survey Ireland mapping, rather than commercial satellite imagery, remains the more reliable guide to what may still be traceable here.