Built around the time when tensions between the O’Connors of Offaly and the Birminghams of Carbury were prompting suggestions for new defensive structures, this unusual diamond-shaped fortress likely served to protect the nearby bridge, just 60 metres to the east. The bridge was crucial for communications between Philipstown (now Daingean), established as the principal strongpoint of the new King’s County in the 1550s, and Trim in County Meath. In 1601, ‘the ward of Castlejordan’ successfully resisted an assault by Sir Rurke Burke, testament to its defensive capabilities.

The fortified house features a distinctive rhomboid ground plan, measuring roughly 9 metres east to west and 8 metres north to south, with circular stair towers at its obtuse northwest and southeast angles. The southeast tower bristles with five gun-loops on the ground floor alone, whilst the main structure’s ground floor contains three more gun-loops and a fireplace in the eastern wall, though notably lacks windows or a barrel vault. The first floor shows more domestic arrangements with small rectangular windows, a fireplace on the south wall, and additional gun-loops covering the northeast angle. Most intriguingly, this structure closely resembles Ireton’s Castle at Lehinch in County Tipperary, suggesting shared defensive architectural traditions of the period.

A substantial bawn wall, approximately 40 metres long and 4 metres high, extends west-southwest from the fortified house, though it’s now overgrown with ivy and shows damage where dressed stone has been removed from embrasures. About 60 metres to the southwest stands a tower house that may have occupied the southwest angle of the original bawn, though a later walled garden now occupies much of this defensive space. By 1640, according to the Civil Survey, the property belonged to Sir John Giffard and included ‘one castle and two mills’ across almost 400 acres, though the castle mentioned likely refers to the nearby tower house rather than this fortified structure.