The rectangular four-storey structure, with its distinctive rounded corners, was originally aligned southeast to northwest before being extended, likely during the latter half of the 16th century. The castle sits strategically above the Kinnegad River, which flows 280 metres to the north, whilst poorly drained peatland stretches to the south and west.

The castle’s history can be traced through various historical documents, though curiously it doesn’t appear on the 1654 Down Survey map of Farbill barony. What the survey does tell us is that these lands belonged to Nicholas Darcy in 1640, who later leased the ‘castle-town, and lands of Rattin’ to James Clarke in 1681. A 2009 geophysical survey revealed fascinating subsurface features that paint a fuller picture of the site’s original defences; a deep trench marks the outline of a levelled bawn wall that once enclosed the castle, with what appears to be a small rectangular gatehouse structure, measuring 12 by 16 metres, positioned at the northern side to guard the entrance.

The landscape around Rattin Castle holds further historical intrigue. Earthworks to the east and the remains of a double-banked causeway to the north represent an old road system that locals in 1837 believed to be an ‘old military road’. This historic route, which once ran west to east through the field north of the castle, is still visible as an earthwork in modern aerial photography, though the road itself has long since been realigned to pass south of the castle. These features, combined with the castle’s imposing architecture and defensive bawn, offer a tangible connection to medieval and early modern Ireland, when such fortified residences served as both homes and strongholds for the Anglo-Irish gentry.