The ground dips and rises in a way that feels almost incidental, yet that subtle shaping of the earth is, in fact, deliberate, ancient, and remarkably intact. What survives here is a rath, the Irish term for a ringfort, the most common type of early medieval settlement monument in the country. These were typically circular enclosures defined by earthen banks and ditches, used as farmsteads by families of some local standing between roughly the fifth and twelfth centuries. The Killonan example was not identified through excavation or documentary research, but through the testimony of crops: aerial photography revealed a cropmark, the faint differential in vegetation colour and growth that appears over buried or disturbed ground during dry summers, tracing the outline of a circular enclosure in the fields below.

The site was recorded and compiled by Denis Power, with details uploaded in June 2013. The monument sits at the base of a west-facing slope, positioned to take in views across the landscape to the north, east, and west, an orientation that would have offered both practical visibility and a degree of natural shelter. Its dimensions are modest but legible on the ground: a circular area roughly twenty-four metres in diameter, defined by a scarped edge approximately one and a third metres wide and thirty centimetres high, with an external fosse, or ditch, running around it. That fosse measures about a metre wide and thirty centimetres deep. Most telling is the causeway that crosses it at the north-east, eight metres wide, marking the original entrance point into the enclosure. The preservation of that causeway is what elevates this from a mere cropmark curiosity to something with genuine physical presence.

The site sits within working farmland, so access would require permission from the landowner. The features are subtle, and a visitor arriving without some preparation may struggle to read the topography clearly. The scarped edge and fosse are most legible when light falls at a low angle, in the early morning or late afternoon, when shadows pick out the slight rises and depressions in the turf. The north-east causeway is the most concrete thing to look for: even a shallow break in an earthwork ditch, consistent and deliberate, communicates something about daily life here more directly than any visible stonework could. The grid reference OS5 2919, near 7512, and the monument's visibility on aerial mapping services, make preliminary orientation possible before any visit.