The circular rath, a type of ringfort defined by an earthen bank and an outer ditch known as a fosse, measures twenty-four metres in diameter and retains enough of its original structure to read clearly in the landscape. The bank is formed from earth and stone, and some inner stone-facing is still visible along the northern arc. The fosse, the defensive ditch that ran around the outside, survives only intermittently, but its presence can still be traced.

A gap of roughly three and a half metres at the east-south-east may represent the original entrance, the point through which people, animals, and goods once passed. Inside, the archaeology becomes more domestic in character. Two house sites are discernible in the western and northern portions of the interior, and internal divisions are still evident in the north-east and south-east quadrants, suggesting the space was carefully organised rather than simply enclosed. Raths of this kind were the farmsteads of early medieval Ireland, typically associated with a single family and their livestock, and this one at Caherglassaun carries those ordinary traces of settled life with some clarity. Notably, a tower house is visible in the background when the site is viewed from the north-north-east, placing the rath within a broader landscape that was occupied and reorganised across several centuries.