Carlow Castle sets on the eastern bank of the River Barrow. It is believed that William de Marshal, Earl of Pembroke and Lord of Leinster built in1207 to1213. Originally the castle was a rectangular block, containing the castle’s principal rooms protected by cylindrical towers at its corners. This castle 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 Today, tow battered towers and part of an intervening wall are all that remain after a local physician tried to remodel it as an asylum in 1814. In an effort to demolish the interior he placed explosive charges at its base and demolished all but the west wall and towers

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. Just the outer face of the west wall and the two neighbouring towers could be preserved.