The site at Cullenagh Beg is a cashel, a type of ringfort defined by a stone rather than earthen boundary wall, and though the drystone construction has long since collapsed into a low, ragged ring, the circular outline of the enclosure is still readable on the ground. At roughly 32 metres in diameter, it would have been a modest but functional defended farmstead, typical of the hundreds of such sites scattered across the west of Ireland.

The interior holds its own quiet puzzles. A series of bumps and hollows suggests that structures once stood within the enclosure, though their precise nature is difficult to determine without excavation. McCaffrey, writing in 1952, recorded the site in its present poor state of preservation, which means the collapse is not recent; this field has looked much the same for generations. Cashels of this kind generally date to the early medieval period, roughly between the fifth and twelfth centuries, when ringforts in stone or earth served as the basic unit of rural settlement across Ireland. The drystone technique, which requires no mortar, was well suited to the limestone-rich landscapes of Connacht, where suitable material lay close at hand.