That arrangement, a religious building enclosed within what appears to be a much older earthwork, is a pattern that turns up across early medieval Ireland, where pre-Christian sacred or defended sites were quietly repurposed as Christianity spread through the landscape.

The enclosure at Monacahee measures approximately 46 metres north to south and 40 metres east to west at its inner extent, defined by an earthen bank up to five metres wide and a flat-bottomed fosse, which is essentially a ditch, running around it. A fosse of this kind was not merely decorative; it formed a clear physical and symbolic boundary between what lay inside and the ordinary world beyond. Beyond that inner fosse lies a berm, a narrow level shelf of ground, and then an outer bank three to four metres wide and rising to between 1.2 and 1.5 metres on the outside. The whole arrangement, inner bank, fosse, berm, and outer bank, stretches to around 63 metres in both directions at its maximum extent. Unusually, the outer bank has been absorbed into a road bank running from the north-west around to the south-east, which may explain why no identifiable entrance survives and why the outer fosse has disappeared entirely. The enclosure's edges have, in effect, been tidied away by later land use, leaving the interior, still overgrown with scrub, as the clearest surviving evidence of what was once here.