It is easy to mistake for a natural undulation, yet the geometry is deliberate, the product of early medieval hands shaping the ground into something that once served as an enclosed farmstead or the seat of a minor local lord. These ringforts, known in Irish as raths, are among the most common archaeological monuments in Ireland, with tens of thousands recorded across the country, yet each one carries its own particular arrangement of banks, ditches, and entrances that rewards close attention.

This example at Killonan was recorded and compiled by Denis Power, with notes uploaded in June 2013. The monument is roughly circular, measuring 31 metres on its northeast to southwest axis and 27 metres northwest to southeast. Its defining feature is a scarped edge, essentially a cut or trimmed slope in the earth rather than a built-up wall, running around the perimeter. Outside this lies a fosse, a shallow ditch, extending from the south around to the northwest, with traces of a low external bank visible at the southwest. What makes this rath particularly legible on the ground are its entrance features: a dip in the scarp at the east-northeast, about two metres wide, and a causeway crossing the fosse at the northwest, nearly six and a half metres across, wide enough to suggest a main point of access. A partial causeway also exists at the southwest. The uneven interior surface hints at shallow quarrying at some point in the site's long afterlife.

The site sits in gently undulating pasture with open views in all directions, which would have suited its original occupants well and still makes the earthwork relatively easy to read once you are standing beside it. Because it sits in working farmland, access would require permission from the landowner. The subtle topography means the monument is best appreciated in low winter light or after rain, when the fosse and scarp cast faint shadows that reveal the circular plan more clearly than summer grass ever does.