To be privately owned
Martello Tower Aughinish

On the Aughinish peninsula in County Clare, Ireland, is the Martello Tower Aughinish. It is one of many Martello towers erected along the Irish coast to defend against invasions.
History+
The Aughinish Tower was constructed in 1811 under the direction of Major Lynch. Originally designed to accommodate an officer and 39 soldiers on the first floor, it served a defensive purpose. In the 1950s, the tower saw an unusual use when the local community utilized it for dance events. In 1960, a Mr. Duffy from Limerick acquired the structure. Later, in 1987, ownership changed hands again to a gentleman from Galway, who converted the tower into a residence.
Source: Wikipedia · Licence: CC BY-SA 4.0
This description draws on the facts documented in the linked Wikipedia article; Wikipedia content is licensed under CC BY-SA 4.0. Wording and editing: Mobile History.
Location: 53.1685, -9.0668