The fort itself is well-defined, a roughly circular enclosure measuring around 43 metres north to south and just over 41 metres east to west, large enough to have sheltered a farmstead and its livestock. What makes the earthworks here particularly legible is the layering of its defences, an inner bank, a fosse, and an outer counterscarp bank, each element still standing to a measurable height after more than a thousand years in agricultural land.

A ringfort, or rath, was the standard form of rural settlement in early medieval Ireland, typically dating from roughly the fifth to the twelfth century. Most were family farmsteads enclosed for security and the management of animals. At Garranereagh, the main enclosing bank still stands 2.4 metres high, with a fosse, a defensive ditch, cut to a depth of 1.6 metres outside it, and a counterscarp bank reaching a further metre beyond that. Stones are visible on the inner face of the bank to the east and south, suggesting the earthen construction was reinforced or revetted with stonework at some stage. The counterscarp bank itself has been partially incorporated into the surrounding field fence system over the years, that slow process by which old structures get absorbed into the working landscape of later centuries. The main entrance, four metres wide, faces east with a causeway crossing the fosse, a characteristic orientation for raths in Ireland; a narrower gap to the north may be a later breach rather than an original feature.