The O’Fallon clan held this stronghold during the Tudor period, with Covaghe O’Failone recorded as owner in 1585 and Redmond O’Fallon in possession just two years later. By 1641, Redmond Mc Redmond Ffallon controlled 500 acres here, though the Cromwellian conquest would see these lands pass to Sir Luke Dowdall. Some historians suggest this might be the site of Onagh Castle, built by the Justiciar in 1236 at Mullach Uanaidhe and attacked by Aedh O’Conchobair in 1270, though the nearby ringwork at Dundonnell seems a more likely candidate for that particular fortress.

Today, visitors encounter an imposing if somewhat puzzling sight: a massive stone cairn, roughly 40 metres across and rising six metres high, conceals much of the original tower keep. The north wall of this keep, measuring 2.5 metres thick, still stands visible at points, offering glimpses of the substantial rectangular structure that once dominated the site, measuring approximately 11 by 8 metres internally. This central tower sits within a distinctive wedge-shaped inner ward or bawn, stretching 75 metres north to south and widening from 30 metres at its northern end to 70 metres at the south. Stone footings and wall spreads mark the bawn’s boundaries, with probable tower positions at the northwest corner and along the southern wall.

The castle’s defences extend beyond this inner enclosure through an eastern entrance with its own causeway, leading to an outer ward that may never have been fully completed. Within the inner bawn, archaeologists have identified four rectangular buildings of varying sizes, including a substantial structure near the entrance measuring 9 by 6 metres internally, and three others positioned strategically around the enclosure. The entire complex predates the surrounding field system, where three more rectangular structures stand 80 to 100 metres to the east, silent witnesses to centuries of habitation, conflict, and eventual abandonment along this quiet stretch of the Ballyglass.