What looks like a modest rise in a field is actually a cashel, a stone-built ringfort, whose concentric layers of limestone rubble, collapsed walls, and carefully positioned entrance survive in considerable detail. Cashels are the drystone counterparts to the earthen ringforts found across Ireland, and this one at Magheraghanrush is a particularly layered example, its 23-metre circular interior ringed by not one but three distinct defensive barriers.

The innermost is a broad rubble limestone bank, nearly four metres wide and still standing to about 0.8 metres internally. Beyond it sits a level berm, then a mostly collapsed drystone wall, then another berm, and finally an outer limestone bank whose low, irregular profile has led at least one specialist, M. A. Timoney, to suggest it may not be original to the structure. The entrance arrangement is worth noting: a narrow break in the inner bank on the southern side aligns with a corresponding gap in the second wall, that gap flanked on both sides by rough un-coursed drystone walling. A third break in the outer bank does not align with these, and is considered a later, probably modern, intrusion. The western third of the interior sits slightly higher than the rest, and within that subtle rise lie the remains of a souterrain, an underground stone-lined passage or chamber that was a common feature of early medieval settlement, used variously for storage, refuge, or both. The site was noted and illustrated by O'Rorke as early as 1890, suggesting it was already considered significant to local antiquarians well over a century ago.