Nothing breaks the surface, no earthwork, no mound, no visible boundary. The only way to see it is from above, and even then only under the right conditions: as a cropmark, the faint differential in how grass or grain grows over a buried ditch betraying the outline of a roughly circular area approximately 75 metres in diameter.

Cropmarks form when buried features, ditches, walls, or pits, affect the moisture and nutrients available to plants growing above them. Crops over a filled-in ditch tend to grow taller and greener; those over compacted foundations stay shorter. The result, invisible at ground level, can emerge clearly in aerial or satellite imagery, particularly during dry summers when the contrast is most pronounced. At Cloncullen, orthophotography from Google Earth and a Digital Globe image taken between 2011 and 2013 revealed the circular ditch outline, along with what appears to be a second, adjoining enclosure immediately to the south-southeast. The site is bisected by a field boundary that post-dates 1700, running northeast to southwest, which means the landscape was already being reorganised into the familiar pattern of modern Irish farmland long before anyone knew there was anything older underneath. The enclosure itself has not been dated, and its original purpose remains unknown; circular enclosures of this kind across Ireland range from prehistoric settlements to early medieval ringforts, the latter being a type of enclosed farmstead common between roughly 500 and 1000 AD.