The tower house sits at the tip of a northwest to southeast spur, with the Annestown stream valley to the east and a ravine carved by a tributary to the west. Though the Le Poer family held the title ‘Baron of Donoyle’ from the early 14th century and were associated with these lands from as early as 1244, the castle itself doesn’t appear in historical records until the 17th century, when John Power owned both the manor and castle in 1641. Local tradition maintains it was an ancient stronghold that eventually fell to Cromwell’s forces during his Irish campaign.

The rectangular tower house measures 10.5 metres east to west and 9.55 metres north to south, featuring a distinctive base batter and cut stone quoins that survive up to the first floor level, except on the eastern wall. Entry was through a doorway on the east wall that led from what was once an entrance lobby into the ground floor chamber, a space measuring roughly 6.3 by 5.3 metres internally. Three embrasures, one still showing its original wicker centering, provided light to this lower level, though their openings are now largely destroyed. The tower’s internal layout included a mural staircase in the south wall, accessed via a passage from the entrance lobby, and another passage in the west wall that led to a loft space beneath an east to west vault. The first floor, now inaccessible, shows only traces of embrasures in three walls, with no evidence of the fireplaces or garderobes typically found in such structures.

Southeast of the tower house stand the remnants of what was likely a small bawn or hall, measuring approximately 10 metres square. Only fragments of the south wall, standing about 3 metres high, and the foundations of the west wall remain; the north and east sides were naturally defended by sheer cliffs dropping some 30 metres. The surviving south wall contains the remains of an embrasure and shows where a round arched gateway once connected to the tower house, with the north side of the arch still visible springing from the tower’s south wall. Today, visitors can reach the castle from the road in the valley below, and nearby Dunhill church lies about 175 metres to the west northwest.