Built sometime in the 16th century, Doonnamona Castle served as both a fortified residence and a symbol of power for the local ruling family. The structure follows the typical design of Irish tower houses from this period, with thick limestone walls, narrow defensive windows, and multiple storeys that once housed living quarters, storage areas, and defensive positions.

The castle's strategic location wasn't chosen by chance; it commanded views across the surrounding countryside, allowing its inhabitants to monitor approaching visitors or potential threats. Like many tower houses of its era, Doonnamona would have been the centre of a small estate, with the surrounding lands providing agricultural income for its owners. The building features the characteristic architectural elements of its type, including a vaulted ground floor that likely served as storage, upper floors accessed by a spiral staircase built into the thickness of the walls, and bartizans (small turrets) at the corners that provided additional defensive capabilities.

Today, the castle stands as a roofless ruin, its walls weathered by centuries of Atlantic storms but still impressively intact. The structure offers visitors a tangible connection to Ireland's medieval past, when such fortified dwellings dotted the landscape, serving as homes to minor nobility and prosperous merchants. Despite its ruined state, enough of the original fabric remains to appreciate the skill of its builders and imagine life within its walls during more turbulent times, when security and status were literally built in stone.