This one in Ballynagallagh, south County Limerick, offers nothing so obliging. The enclosure exists, as far as the record is concerned, as a faint oval shadow pressed into a field, visible only from the air and only under the right conditions. It has never been marked on any Ordnance Survey historic map, and by the time satellite imagery began routinely capturing this stretch of improved pasture on the south-western edge of boggy moorland, the mark had faded entirely from view.

The enclosure came to official attention in 1986, when the Bruff aerial photographic survey picked out a roughly oval-shaped cropmark in the landscape below. Cropmarks of this kind appear when buried features, such as the ditches or foundations of an old enclosure, affect the moisture and nutrient content of the soil above them, causing overlying crops or grasses to grow at a slightly different rate or colour. That differential, invisible at ground level, can resolve itself into legible geometry when seen from altitude under dry conditions. The site sits in wet, low-lying pasture, about 800 metres south of Lough Gur, a lake long recognised as one of the most archaeologically significant areas in Ireland, with prehistoric settlements, stone circles, and ring-forts clustered around its shores. Ballynagallagh itself lies just fifty metres south-west of the boundary with Loughgur townland, and at least two further enclosures have been recorded within 175 metres to the south and south-south-west. The boggy ground to the north-east appears on older maps under the annotation Red Bog, though the enclosure itself goes unrecorded on those same sheets.

There is nothing to see at ground level, and that is more or less the point. The site sits in working agricultural land on the south-western fringe of moorland, and subsequent orthoimagery, including Ordnance Survey captures from 2005 to 2012, a Digital Globe image from 2011 to 2013, and a Google Earth image from March 2017, has failed to recover the cropmark that the 1986 survey briefly revealed. Visitors drawn to the wider Lough Gur area, which rewards a separate and substantial visit, might note that this unremarkable field represents a fairly common condition in Irish archaeology: a monument catalogued, located with some precision, and yet stubbornly absent from any view available to the human eye at the surface.