The ground surrounding the medieval structure appeared unusually raised on three sides; to the east, south, and west. O’Rahilly suspected these earthworks might be the remains of a bawn, a fortified courtyard wall that once defended the castle. Such defensive structures were common features of Irish castles, providing an outer layer of protection for the inhabitants and their livestock during turbulent times.

Historical records support O’Rahilly’s theory about the site’s former grandeur. The Civil Survey of 1654-56, a comprehensive land survey conducted after Cromwell’s conquest of Ireland, provides a snapshot of Castletroy in 1640. According to the survey, Theobald, Lord Baron of Brittas, owned the property then known as ‘CallaghItroy’, which consisted of a ruined castle, an orchard, and an eel weir on the river. The mention of an orchard is particularly interesting, as it may refer to what was actually a walled garden or the bawn itself, spaces that often served multiple purposes in medieval Irish estates.

Today, visitors to Castletroy will find little obvious evidence of the bawn that once stood here. The defensive walls have been levelled by centuries of agricultural use and development, leaving only subtle changes in ground elevation as clues to the castle’s former defences. Yet these gentle rises in the earth tell a story of a time when Castletroy was more than just ruins; it was a fortified residence complete with protective walls, productive gardens, and river fishing rights, all essential elements of a thriving medieval estate.