A U-shaped enclosure in the wet pasture of Dromkeen South, County Limerick, exists in the record for a single reason: a brief window of aerial observation in 1986 during which the crop or soil conditions happened to be exactly right. Before that moment, there is no trace of it on any historical Ordnance Survey Ireland map. After it, the site has disappeared again entirely, invisible on aerial orthoimages captured in 2005, 2006, 2007, through to 2012, invisible again on Digital Globe imagery from 2011 to 2013, and invisible once more on Google Earth imagery taken as recently as June 2018. It exists, in practical terms, as a photograph of a shadow.

The enclosure was identified during the Bruff aerial photographic survey, logged as Bruff 50 and referenced under aerial photograph 4/3717. At that moment it appeared as a U-shaped form lying adjacent to a stream, close to the townland boundary between Dromkeen South and Dromkeen itself. Roughly 45 metres to the south-east sits Gortavalley Fort, a ringfort recorded under the site number LI024-002. Ringforts, sometimes called raths, are roughly circular enclosed settlements that were common across Ireland from the early medieval period, typically defined by an earthen bank and ditch. Whether the enclosure at Dromkeen South relates in any functional or chronological way to Gortavalley Fort is simply not known. The record, compiled by Edmond O'Donovan and uploaded in September 2020, is careful not to speculate beyond what the single aerial image confirms.

The site sits in wet pasture, which itself offers a partial explanation for its intermittent visibility. Soil and crop marks of this kind tend to appear only when subsurface features affect ground moisture or plant growth in ways that happen to coincide with the right season, the right crop, and the right angle of light. On the ground, there is likely nothing obvious to see. Locating the approximate area is possible using the townland boundary as a reference and bearing in mind the proximity to Gortavalley Fort to the south-east, though access to private farmland would require the landowner's permission. The most instructive version of this site remains the 1986 aerial photograph itself, which captures something the landscape has since reclaimed entirely.