Grace O'Malley's or Kildavnet Castle is actually a 15th century Tower House. The O'Malley's were a powerful seafaring family.
Grace became a feared leader and gained fame as a sea captain and pirate. She is reputed to have met with Queen Elizabeth I in 1593. She died around 1603 and is believed to be buried in the O'Malley family tomb on Clare Island. Kildavnet or Kildownet Tower house is located on the south-eastern shore of Achill Island. The placename literally means “the small church of Davnet” and refers to the 7th century Saint Dympna who built a small church here. However it is best known as the home of its most famous tenant, the legendary pirate queen Granuaile. Kildavnet Castle is a couple of hundred metres along the shore from the ancient Kildownet Church. This three-storey building stands about 12m (40ft) tall and has buttress fortifications at the top. It is vaulted above the first floor, and a hole at the corner of this vault is the only access to the higher levels. The Tower stands at a strategically important spot, guarding the waters of Achill Sound which links Clew Bay to the south with Blacksod Bay to the north. During the time of Granuaille it was one of several such strongholds that she controlled, including the Tower House on Clare Island and Rockfleet or Carraigahowley Castle near Newport.