Donegal Castle is a castle situated in the centre of Donegal Town in County Donegal in Ulster, the northern province in Ireland. The castle was the stronghold of the O'Donnell clan, Lords of Tír Conaill and one of the most powerful Gaelic families in Ireland from the 5th to the 16th centuries. For most of the last two centuries, the majority of the buildings lay in ruins but the castle was almost ... Wikipedia