This castle is often associated with Shakespeare's Macbeth because the title character was the Thane of Cawdor. The connection, however, is pure artistic license—Cawdor's enormous tower was built in about 1450, several centuries after the real Macbeth.
Thanks to a fortuitous marriage, Cawdor Castle passed to the ownership of the Campbells of Argyll in 1510, and they did a lot to expand the edifice. Legend has it that as long as a "red-haired maiden" can be found near Loch Awe, Argyllshire, the castle shall forever be in the hands of the Campbells. (13 percent of Scots have red hair, compared to 2 percent elsewhere, so things look good for the Campbells.)