Once standing near the western shores of Lough Conn, its exact location remains uncertain, though evidence suggests it occupied the ground where Castlehill House, a 19th century country house, now stands. When workers began constructing this Georgian residence in the 1830s, they uncovered substantial foundations and rubble from the old fortification, providing tangible proof of the castle’s existence despite its absence from both the 1838 and 1922 Ordnance Survey maps.

Local tradition speaks of two castles here, one occupied by William Barrett and the other by Richard Barrett, both of which later passed to the Cormack family before their line died out. The Annals of the Four Masters provides a dramatic account of the castle’s demise in 1526, when the formidable Hugh O’Donnell marched his army into Connacht at the request of Richard Burke’s descendants. O’Donnell captured both this castle, known then as Caorthanan, and the nearby castle of Crossmolina, seizing hostages and spoils before deliberately demolishing both strongholds to render them permanently uninhabitable. His destructive campaign ultimately helped broker peace between the Burke descendants and the Barretts.

Today, visitors to Castlehill House might spot the last physical traces of the medieval fortress; several carved stones salvaged from the castle ruins were incorporated into the garden buildings during the Victorian era. These weathered fragments serve as the only visible reminder of a fortification that once played a role in the complex territorial disputes and clan warfare that shaped medieval Mayo, before O’Donnell’s army reduced it to rubble nearly five centuries ago.