It has a lopsided design with only one projecting tower to protect the approach along a narrow ramp from the south-west. The stone curtain wall of the outer bailey is likely to have been built by the Mac Artáin chiefs of Kinelarty, who owned Dundrum in the late 15th century. At some point after 1333 it was managed by their cousins the Magennis clan, and is sometimes called "Magennis Castle". The Earl of Kildare briefly captured the castle in 1517 as did Lord Deputy Grey in 1538.. Phelim Magennis Mac Artáin and his son Donal Oge Mac Artáin later surrendered the castle to Lord Mountjoy in 1601. It was made over to Lord Cromwell in 1605 and sold to Sir Francis Blundell in 1636. The Mac Artáin clan were possibly regranted the castle at Dundrum, but later had it repossessed by the Parliamentarians, who dismantled the castle in 1652 after they withdrew their garrison. After 1660 the Blundells returned and built a gabled L-shaped mansion in the south-west corner of the outer bailey. This dwelling was ruined by the time the property passed to the second Marquess of Downshire in the early 19th century, though the trees on the hill were probably planted at this time. The castle and grounds were placed in State Care by the seventh Marquess in 1954. The castle is an important example of Norman architecture, and is a regular destination for tourists and school children. It was the subject of an episode of archaeological television programme "Time Team", broadcast on 24 February 2013. An unrelated structure called Dundrum Castle existed near Dundrum, County Tipperary and was the family seat of the O'Dwyer's of Kilnamanagh, members of the Gaelic aristocracy. Following the invasion of Ireland by Oliver Cromwell and the ill-fated retributive capture of the Rock of Cashel by the last clan chief Philip O'Dwyer, the O'Dwyers lost their properties per the Act of Settlement 1662. Dundrum Castle was destroyed sometime afterwards. In 1730 a mansion known as Dundrum House was built on the site. Dundrum House served as the home of Cornelius Maude, Viscount Hawarden and his descendants until the early 20th century when the structure was sold to an order of Roman Catholic nuns. Transferred to private owners in 1978, Dundrum House now serves as a luxury hotel and golf club.