It does not appear on historic maps. It does not show up on aerial photography taken as recently as 2015. What it amounts to, for now, is a cropmark, the faint trace left in vegetation when buried structures alter the moisture or nutrients available to whatever grows above them, and a question mark over what that trace actually represents.

The site came to light in 2000, when Michael Connolly, County Archaeologist for Kerry County Council, was assessing a forty square mile area north of Killarney to help determine a road route. In the course of that survey, he identified what appeared to be the cropmark of an oval enclosure at Cloonydonigan and reported it accordingly. Oval enclosures of this kind are often associated with early medieval settlement in Ireland, sometimes forming the boundary of a farmstead or a place of some local significance, though without excavation or clearer evidence it is impossible to say what this particular feature might have been. The difficulty is that the site sits within a commercial forestry plantation described as impenetrable, and the plantation had not yet been thinned at the time it was assessed. The closest anyone can get to the likely location is within roughly eighty metres, and even that approach is more navigational estimate than confirmed access.

What makes Cloonydonigan quietly unusual is precisely its elusiveness. Most archaeological sites exist in some tension between what is known and what is guessed, but this one sits at an extreme end of that spectrum. The feature has been neither confirmed nor ruled out. It leaves no trace on the maps that might otherwise have preserved some memory of it, and the trees planted above it have, for now, made it effectively inaccessible to further investigation.