It is the home of the Duke and Duchess of Argyll and their children. The castle was designed by Sir John Vanbrugh for the great second duke in 1720. Construction began in 1746. The fifth duke saw the castle's completion in 1789. The castellated towers were part of the original building but it was considered less impressive than the original castle once located on the same site--more a mansion than a castle--so the conical towers were added later to give it a more "castle-like" appearance.
As I mentioned, an original castle once stood on the same site, built by the Campbell Earls of Argyll during the 15th century. It was eventually destroyed by fire during the Civil War of 1644 by the Marquis of Montrose.
My novels are partially set in this beautiful place. There's a lot more to tell you about it but I thought you might enjoy a picture tour instead.