This one leaves almost no trace at ground level at all. In a field of reclaimed pasture in Ballynacourty, County Limerick, a circular earthwork roughly 34 metres in diameter has been so thoroughly levelled by centuries of agricultural activity that it is essentially invisible to anyone walking across it. The only reliable way to see its outline is from above, where the buried remains betray themselves through differential plant growth, producing what archaeologists call a cropmark, a faint discolouration in the vegetation that follows the ghost of the original structure.

The site was identified as an enclosure by archaeologist Brian Hodkinson in 2003, sitting approximately 90 metres to the north-east of a nearby castle. Despite its proximity to a recorded monument, it never appeared on Ordnance Survey Ireland historic maps, meaning it went uncharted through the whole period of systematic Irish cartographic survey. Its existence became clearer when a Digital Globe orthoimage, a georeferenced aerial or satellite photograph, captured a roughly circular cropmark at the location sometime between 2011 and 2013. A further image taken from Google Earth on 28 June 2018 showed the cropmark still faintly legible, though the earthwork itself had by then been almost entirely reduced. The site was compiled into the archaeological record by Martin Fitzpatrick and uploaded in November 2021.

There is little to see on the ground, and that is rather the point. The surrounding land is working pasture, and access would require landowner permission. Anyone with a serious interest would do better to begin with the Google Earth orthoimages referenced in the site record, where the circular form is at least partially readable. Cropmarks of this kind tend to show most clearly during dry summers, when moisture stress affects the grass or crops growing over buried ditches and banks differently from the surrounding soil. The nearby castle, which does appear on the historic maps, provides useful orientation. The earthwork itself sits quietly to its north-east, beneath the surface of a field that gives no hint of what lies underneath.