The ringfort that conceals it sits on a modest rise in the Sligo landscape, a circular earthwork barely visible unless you know what you are looking at, yet it carries within it a souterrain, an underground stone-lined tunnel or chamber typically used in early medieval Ireland for storage, refuge, or both. That combination, an above-ground enclosure with a subterranean annex, tells you this was a settlement where someone took considerable trouble over security and practicality.

The earthwork itself is a rath, the most common form of ringfort in Ireland, built from earth rather than stone. At Magherabrack, the raised interior platform measures roughly 28.7 metres across from north to south, enclosed by an earthen bank about 5.5 metres wide and standing 1.3 metres above the interior ground level. Beyond that bank lies an infilled external fosse, a defensive ditch, originally between three and four and a half metres wide, and beyond that again a low counterscarp bank, a secondary outer rampart still traceable along the south-west to north-west arc of the site. The interior slopes gently downward from north-west to south-east. On the eastern side of the enclosing bank, a break roughly two metres wide, now partially blocked up, marks the original entrance. These details, the layered defences, the carefully positioned gateway, the souterrain within, point to a community that was far from passive about its own protection. Raths of this kind are generally dated to the early medieval period, roughly the fifth to twelfth centuries, and would have served as the enclosed farmsteads of local farming families, occasionally of higher social rank.