The enclosure here is roughly circular, measuring about 25 metres north to south and 26 metres east to west, and the builders cut into the slope itself along its eastern and southern edges to achieve a flat interior. That deliberate levelling, combined with the care taken in constructing the boundary, suggests this was not a casual or temporary arrangement.

The enclosure boundary is itself a composite thing, assembled from at least three distinct elements depending on which arc you are following. Along the south-southwest to northwest section, a contiguous line of orthostats, upright standing stones set edge to edge like a low stone wall, forms the primary enclosure; these stones stand roughly a metre high. From the northwest around to the northeast, the boundary drops to a low scarp in the natural ground. Then, continuing from the northeast around to the east-northeast, a narrow earthen bank takes over, faced externally with large slabs set closely together and reaching about 0.75 metres in height. On that same northeastern to east-northeastern stretch, there is also a possible external fosse, a shallow ditch, roughly 0.85 metres deep, which would have added both a physical and a symbolic barrier to the outside. Enclosures of this general type are a recurring feature of the Irish landscape, serving at various periods as farmsteads, ceremonial spaces, or places of assembly, though the specific function of this one at Monavaddra remains unresolved.

The site sits on a north-northwest-facing slope, which is a relatively unusual orientation and would have kept much of the interior in shade through a good part of the day. Whether that was a practical consideration or simply where the builders chose to work is not recorded anywhere.