The enclosure measures approximately 38 metres north to south and 32 metres east to west, making it a substantial example of a rath, the Irish term for a ringfort, which was the most common form of rural settlement in early medieval Ireland. These were typically the enclosed farmsteads of farming families, their earth banks offering a degree of protection for people and livestock rather than any serious military defence.

The earthwork at Largan is defined by an interior bank and an external fosse, a ditch dug around the outside to provide the material for raising the bank. Traces of a second, outer bank are still visible to the west-northwest, a feature that would have given the enclosure an additional layer of definition and perhaps status, since multiple enclosures are sometimes associated with higher-ranking households. A gap on the eastern side may represent the original entrance, a positioning that is common in ringforts across Ireland and may reflect practical, symbolic, or orientation-related preferences among their builders. The site was noted by Killanin and Duignan as early as 1967, and its condition at that time, and apparently since, speaks to how well earthworks can survive when left undisturbed in agricultural land.