What survives here is a cashel, a type of ringfort enclosed by a drystone wall rather than an earthen bank, roughly circular in plan and approximately forty metres across. It is poorly preserved, and the modern field wall that cuts across it at the north-east and south-west has not helped matters. To the north-west, the original wall has vanished entirely, leaving no surface trace at all.

Cashels of this kind were typically built during the early medieval period, roughly between the fifth and twelfth centuries, and served as enclosed farmsteads for a single family or small kin group. The drystone construction places this example within a wider tradition of building in stone-rich landscapes across the west of Ireland, where suitable timber was scarce but limestone and granite were plentiful. What makes the Ballydonnellan site quietly interesting is not the cashel wall alone, but the presence of two circular house foundations lying roughly thirty metres to the east and north-east. These separate structures suggest activity extending beyond the enclosure itself, hinting at the kind of dispersed, small-scale settlement pattern that characterised rural life in early medieval Connacht.