The earliest written record of this castle is from 1231 but it does not name its builder. It is widely assumed that the castle was built by
William Marshal the elder in the time period between 1207 and 1213 which he spent in Ireland. The castle in Carlow was the very first of its kind in Ireland, a towered
keep, where a huge rectangular tower is surrounded by four smaller three-quarter-circular towers at the corners of the rectangle. Similar castles of the same period were erected in
Ferns,
Lea, and
Terryglass. the towers had a diameter of , and the walls were thick. and two latrines. The latter indicates that the space was divided. The entrance door was in the first floor but is now broken out. The castle was handed over to the crown in 1306, granted in 1312 to
Thomas Plantagenet, confiscated by the crown in 1537 as the landlords were absent, bought by the
Earl of Thomond in 1616, changed hands multiple times until it was taken by
Oliver Cromwell in 1650 but was later returned to the Earl of Thomond. In 1814 the castle was widely destroyed in an attempt to create more space for the conversion into a lunatic asylum with the help of
explosives. == Literature ==