This rectangular earthwork, measuring approximately 40 metres by 30 metres, consists of a raised platform surrounded by a water-filled ditch; a defensive feature that would have protected a timber manor house or farm complex during the 13th and 14th centuries. Unlike the stone castles built by wealthier lords, these moated sites were the rural strongholds of lesser nobility and prosperous farmers who needed protection whilst establishing themselves in newly colonised territories.

The site at Castlereagh follows the typical pattern of Irish moated sites, with its platform raised about two metres above the surrounding land and enclosed by a ditch that’s roughly six metres wide. Archaeological evidence from similar sites across Ireland suggests that the central platform would have supported timber buildings, including a hall house, agricultural structures, and possibly a small chapel. The moat served multiple purposes; it provided defence against cattle raids and local disputes, drainage for the platform, and a source of fresh fish for the household.

Today, the earthworks remain clearly visible in the landscape, though centuries of agriculture have softened their edges and the moat now only holds water seasonally. Castlereagh’s moated site is one of over 200 such monuments recorded across Ireland, with particular concentrations in counties Dublin, Meath, and Cork. These sites represent an important phase in Irish history when new agricultural practices, land ownership patterns, and defensive architecture were introduced by Anglo-Norman settlers, fundamentally reshaping the medieval Irish countryside.