Donegal Castle () is a castle situated in the centre of Donegal Town in County Donegal in Ulster, Ireland. For most of the last two centuries, the majority of the buildings lay in ruins but the castle was almost fully restored in the early 1990s. The castle consists of a 15th-century rectangular keep with a later Jacobean style wing. The complex is sited on a bend in the River Eske, near the mouth of Donegal Bay, and is surrounded by a 17th-century boundary wall. There is a small gatehouse at its entrance mirroring the design of the keep. Most of the stonework was constructed from locally sourced limestone with some sandstone. 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. History Donegal (), translates as Fort of the Foreigner possibly coming from a Viking fortress in the area destroyed in 1159. However, due to hundreds of years of development, no archaeological evidence of this early fortress has been found. Hugh Roe I O'Donnell, wealthy chief of the O’Donnell clan, built the castle in 1474. At the same time, he and his wife Nuala built a Franciscan monastery further down the river. A local legend tells of a tunnel connecting the two but no evidence for this has been found. The castle was regarded as one of the finest Gaelic castles in Ireland. This was indicated by a report by the visiting English Viceroy, the Lord Deputy of Ireland, Sir Henry Sidney, in 1566, in a letter to William Cecil (created The 1st Baron Burghley in 1571), the Lord High Treasurer, describing it as "the largest and strongest fortress in all Ireland", adding: "it is the greatest I ever saw in an Irishman's hands: and would appear to be in good keeping; one of the fairest situated in good soil and so nigh a portable water a boat of ten tonnes could come within ten yards of it" In 1607, after the Nine Years' War the leaders of the O'Donnell clan left Ireland in the Flight of the Earls. In 1611, during the Plantation of Ulster, the castle and its lands were granted to an English Captain, Basil Brooke. The tower house was severely damaged by the departing O'Donnells to prevent the castle from being used against the Gaelic clans