Situated high above the Avon Water, in the grounds of Chatelherault Country Park, Cadzow Castle lies 2 miles (3 km) southeast of the centre of Hamilton in South Lanarkshire. Now maintained by Historic Scotland, Cadzow Castle was most-likely built in the 12th Century and became a royal residence for Alexander II and Alexander III. A previous structure here is said to have been a hunting lodge of the ancient kings of Strathclyde. The castle was rebuilt around 1530 by Sir James Hamilton of Finnart (d.1540), for his half-brother James Hamilton, the 2nd Earl of Arran (1516-75). Arran opposed the marriage of Mary, Queen of Scots, to Lord Darnley and Mary confiscated his castles and briefly sent Arran into exile. However, soon reconciled with Mary, it is here that she stayed after her dramatic escape from Loch Leven Castle in 1568.
In 1572, Arran fortified Cadzow against the Protestant Regents who ran the country on behalf of James VI, but they attacked the castle in 1579, and following a brief siege, it was captured and destroyed by explosives. It was never re-occupied, but was partially rebuilt c.1820 by Alexander, the 10th Duke of Hamilton (1767 - 1852) to act as a picturesque folly within the parkland of Hamilton Palace.
Considerable ruins remain, comprising a strongly-constructed keep with drum towers at the southwest and southeast. Rubble fills the walls, lying over vaulted chambers which have been the subject of archaeological investigation (2000-04).