Carlow Castle is situated on the banks of the River Barrow near Carlow town centre, in County Carlow, Ireland. It was formerly one of the most impressive Norman castles in Ireland, but only the western wall and two towers survive. The castle is now the imposing centrepiece of a major urban renewal programme.
The original keep was a three-storey rectangular structure with cylindrical corner towers. It was probably built between 1207 and 1213 by William Marshall on the site of a motte erected by Hugh de Lacy in the 1180s. It may be the earliest example of a four-towered keep in Britain or Ireland. The entrance is at the first-floor level in the north wall and access to all storeys, which had timber floors, was by way of stone stairways in the thickness of the west wall. Ownership of the castle passed to the Crown in 1306 and was later granted to the Earls of Norfolk, who retained it until confiscation in 1537. James FitzGerald captured it in 1494, and it was taken again by Silken Thomas in 1535, and changed hands a number of times before being purchased by Donogh O'Brien, Earl of Thomond in 1616. It fell to the Confederates during the Irish Confederate Wars in 1642. In that year, a detachment from the Duke of Ormond's army rescued 500 starving English prisoners from the castle. The Castle was later returned to Thomond after being liberated by Henry Ireton in 1650. It later passed to the Hamilton family.
In 1813, the Hamilton family leased the castle to a physician, Dr. Philip Parry Price Middleton, who spent £2,000 in an effort to make it habitable as a lunatic asylum. On 13 February 1814, in attempting to create an underground passageway using dynamite blasting powder, the eastern wall collapsed and brought down the east towers and adjoining walls. The stonework was subsequently broken up and carted away from the site.