This ancient ruined castle is found five miles south of Fermoy.
It was built by David Barry, the first Earl of Barrymore in the 17th century. Constructed on the site of an older castle, it was the Irish residence of the Barrymores until 1771 when it was burnt down in an accidental fire.
In its prime, the castle grounds were very beautiful. To the north a terraced garden was constructed. On the west side the water was harnessed to create an artificial lake. This was bounded by a garden. To the west and south a deerpark surrounded by high walls of stone was laid out. This gave rise to the townland of Deerpark.
The stables and the barns were built near the castle at a point since known as Stables Cross. To complete the work a broad and straight road was built in front of the castle and extended from Stables Cross to Spuree Cross. This is now the public road and Main Street of Castlelyons.
The castle was destroyed by fire on 22nd July 1771. The fire was attributed to two men who were repairing the roof when a piece of soldering iron set the wooden beams alight.
The fire smouldered in the ruined castle for three months. No effort was ever made to restore the building and what remained of the castle and its gardens fell into decay.