Recorded separately from the tomb itself is an enclosure, a distinct archaeological feature that sits in the same townland but tends to be overlooked entirely in the shadow of its more famous neighbour.

Enclosures of this kind, typically defined by a stone wall, earthen bank, or fosse forming a roughly circular or oval boundary, appear throughout the Irish landscape in contexts ranging from the Bronze Age to the early medieval period. On the limestone karst of the Burren, where the bare grey pavement makes surface features unusually legible, such boundaries can sometimes be traced with particular clarity. The Poulnabrone area has long been understood as a place of significance across multiple prehistoric periods; excavation of the portal tomb itself in the 1980s revealed the remains of at least sixteen individuals deposited there over a span of several centuries during the Neolithic. The presence of a separate enclosure in the same locality adds another layer to what was evidently a meaningful and repeatedly used place in the prehistoric landscape of County Clare, though the precise date and function of this particular feature remain, for now, undocumented in any publicly available form.