This castle is probably one of the most remarkable castles in Scotland. The castle is circular with four great round towers protruding from the battlements and also a square tower keep. The castle was built around 1204. The castle was thought to have been a regular target of the Vikings who in 1228, Uspak the Viking leader attacked the castle in force, however it was successfully defended with med-evil defences such as boiling oil, pitch or lead. However the invaders returned in the same year with wooden platforms and managed to breach the walls. The castle was then held by the Vikings despite many attacks until the battle of Largs in 1263 at which time the castle returned to the hands of the Scots.
In the late 14th Century Robert 2nd strengthened the defences and in particular the curtain wall. Robert 3rd actually lived in the castle followed by his son the 1st Duke of Rothesay. The Stewarts became keeper of the castle in 1406 on the death of Robert 3rd.