The original wooden castle was destroyed in the late 13th century and replaced with the current stone structure. More than £875 was spent on works from 1274 to 1295, overseen by John de Lydyard. The current structure consists of a 40-metre-wide courtyard enclosed by curtain walls and a ditch.
The walls are up to 2.5 meters thick in parts. The castle was originally surrounded by a river to the east and a moat on the other sides. While it does not have a keep, the main residence is a three-story rectangular gate building to the north, complemented by two three-quarter round towers, one to the south west and one to the south east.
The south-western tower, known as the Ormond Tower, contains a first floor room with a fireplace on the north wall and a 17th-century plasterwork coat of arms. The south-eastern tower, referred to as King John’s Castle, is taller, with 3 storeys. The original gate building is dated to around 1280 but the current stone structure was built by the 4th Earl of Ormond in the 15th century.
The gate building is approximately 27 meters high and originally included a bascule bridge and portcullis. The entrance has a barrel vault ceiling. Below the gate tower is a basement prison which was accessible by trapdoor. In the 17th century, a second-floor living area was added to the building including a pointed groined vault, three bays, lancet windows, a garderobe, a chimney stack, a large hooded dog-tooth capital fireplace on the southern wall, and crow-stepped gables.