Built sometime in the 15th or 16th century, the castle likely belonged to the O’Brien clan, who dominated much of Clare during the medieval period. The rectangular tower, though now roofless and partially ruined, still rises four storeys high, its walls punctuated by narrow defensive loops and the remnants of window openings that once offered commanding views across the surrounding countryside.

The castle’s location was no accident; from this elevated position, its occupants could monitor movement along the ancient routeways that connected the Shannon region with the interior of Munster. The structure itself follows the typical design of Irish tower houses of the period, with thick walls tapering as they rise, a spiral staircase built into the corner, and vaulted ceilings over the lower floors for added strength and fire resistance. Archaeological evidence suggests the castle remained occupied well into the 17th century, though it likely fell into decline following the Cromwellian conquest when many such fortified residences were deliberately slighted or abandoned.

Today, Castle Doon stands as a quiet sentinel above the lake that shares its name, accessible via a short but steep climb from the roadside. The ivy that clings to its weathered walls has helped preserve some of the stonework, whilst also giving the ruins a romantic quality that draws photographers and history enthusiasts alike. Local tradition holds that the castle’s stones were later quarried for use in nearby farm buildings, a common fate for many of Ireland’s medieval structures, though enough remains to give visitors a sense of what life might have been like for the minor nobility who once called this windswept tower home.