It is not the sort of place that announces itself. The enclosure measures roughly 25 metres in diameter and is defined by a fosse, a cut ditch, about 4 metres wide, though the whole thing is poorly preserved, softened by time and the damp conditions of its setting. What makes it quietly odd is that combination: a deliberately constructed, slightly domed interior placed in low-lying, waterlogged terrain, where you might least expect someone to have gone to the trouble.

Circular enclosures of this kind appear across Ireland in various forms and periods. Some served as ringforts, the enclosed farmsteads of early medieval Ireland; others were ceremonial in function, or acted as boundaries for settlements or livestock. The waterlogged valley setting at Mattymount does not rule out any of these possibilities, but it does complicate them. Building and maintaining a fosse in marshy ground would have required real effort, and the slightly raised interior suggests some attempt to keep the enclosed space usable and dry. Without excavation, the date and precise purpose of the Mattymount enclosure remain open questions.