The original castle was built around 1098 by Magnus Barelegs the Viking who came to conquer the Scottish islands. (Magnus was called “Barelegs” because he wore the kilt in the tradional Scots manner.)
Later, the castle fell into Scottish hands, but was attacked by Vikings in 1230 and again in 1263 when it was captured by King Haakon who was subsequently defeated at the Battle of Largs.
It was a favourite residence of Robert II, whose son made Rothesay a royal burgh in 1401. James V added the part known as The Palace.
Rothesay Castle remained strategically important through to the 17th century when it was held for King Charles and then Cromwell. The Roundheads partially destroyed the castle when they abandoned it in 1659. A few years later as part of the 1685 rebellion it was set on fire by the Argyll Highlanders.
The castle was partially restored by The Marquis of Bute in 1816, and today is in the stewardship of Historic Scotland
There is street parking nearby, and the cache is within easy walking distance of the ferry terminal. You do not have to enter the grounds of the castle to find the cache, but you may find that you want to visit the castle once you see it.
The cache is a small magnetic nano, too small for a pen or pencil. Watch you don't drop it in the moat when you replace it!