Rothesay Castle was built by the Stewart family in the 1200s as a defence against invading Vikings.
Walk around its great moat to get the best view of Scotland's only circular curtain wall and four round watchtowers.
Inside, the great hall features displays about the castle's history and its regal heritage.
Rothesay Castle played a key role in the Scottish Wars of Independence and the English Civil War. Both Robert the Bruce and Cromwell occupied the castle.
Image: Visit Scotland / Paul Tomkins