What survives of this cashel, a type of ringfort built from drystone walling rather than earthen banks, traces a circuit roughly 33 metres in diameter, but the south-eastern arc has been lost entirely to land reclamation. What remains is further obscured by field-clearance rubble, the accumulated debris of generations of farmers tidying stones off the surrounding land and depositing them against, or on top of, the very structure they were unwittingly burying.

Cashels of this kind were typically built during the early medieval period in Ireland, functioning as enclosed farmsteads for individual families or small communities. The drystone construction was particularly common in areas of the west where stone was plentiful and timber comparatively scarce. At Ardgaineen, the enclosure has not been left entirely to archaeology. A later field wall cuts across or through the interior, and a small animal shelter has been built within it, meaning the site has continued to be used in a low-key, practical way long after its original purpose was forgotten. This layering of use is visible in the fabric of the place itself, the early medieval boundary quietly absorbed into the working landscape of more recent centuries.