Kildavnet or Kildownet (Cill Dambhnait in Irish Gaelic) Castle is located on the south-eastern shore of Achill Island, overlooking the waters of Achill. The placename literally means “the small church of Davnet” and refers to the 7th century Saint Dympna who built a small church here. The castle is said to have been built by the O’Malley Clan in about 1429. However it is best known as the home of its most famous tenant, the legendary pirate queen Granuaille (Grace O’Malley).
Kildavnet Castle is a couple of hundred metres along the shore from the ancient church for which it is named. It is a fine example of a 15th-century Irish rectangular tower house. This three-storey building stands about 12m (40ft) tall and has buttress fortifications at the top. There is no stairway from the ground or first floor levels and access to the upper storeys is not possible. It is vaulted above the first floor, and a hole at the corner of this vault is the only access to the higher levels.