Sketrick Castle, Sketrick Island, Ballydorn, Killinchy, Co Down, BT23 6QH

Sketrick Castle is a ruined four storey tower house situated on the eastern shore of Sketrick Island near Ballydorn, County Down, next to a causeway connecting the island to the mainland. The castle is believed to date from the 14th or 15th century.

The structure is built of split stone rubble in rectangular plan, measuring approximately 16 metres by 9 metres. At its highest point the walls rise to 17.5 metres and are 1.4 metres thick. The eastern wall survives largely intact and contains several narrow openings. Little of the northern wall remains standing, and almost nothing survives of the southern and western walls. The outlines of various chambers and entrances are still discernible within the ruin, including narrow chambers on the north side and the remains of a vaulted stone first floor. The staircase apparently rose through the eastern wall. There are traces of what appears to be a chimney piece on the second floor at the north-east corner. A low bawn wall extends to the north and east, and a narrow stone-lined trench, partly covered and carrying spring water, runs along the eastern side.

The castle first appears in historical records in 1470, when the Annals of the Four Masters record that it was captured by Henry O'Neill and handed to the head of the MacQuillans, whose ancestors may have originally built the castle. An early 16th-century crown survey of ordnance notes that the Earl of Kildare had brought artillery to Sketrick Castle. The castle was captured in 1556 by John Prowse, constable of Carlingford Castle. In the later 16th or early 17th century it came into the hands of the Savages of the Ards, whose descendants held the island until the 1800s.

The Ordnance Survey Memoirs of 1833 describe the castle as "a plain square building, 40 feet high" with an entrance on the west face, but note it was already "unroofed and open from the top to the ground". The structure remained largely unchanged until 1896, when the south-western angle collapsed catastrophically, reportedly shaking the castle and raising a tall column of white dust. The castle is now in state care.