In Scotland the word castle denotes a variety of structures. In most cases, one will not find castles that fit the usual concept, that of crenellated (square indentations, or openings) battlements and towers. Remember that the idea of a castle was a fortified structure (castle – from the Latin castellum, fortress), and the fortified structures of Scotland take many a form.
   The evolution of castle design and building in Scotland began with the motte and bailey. These were a fortified hill (motte)  on which was built a keep of wood or stone, overlooking the bailey, an enclosed courtyard usually surrounded by a wooden palisade.
   These gave way to tower houses, stone buildings of several stories, windowless on the ground floor for defensive purposes. Numerous tower houses remain today, many of them used as a residence or rental property. Often defending walls, courtyards and other wings were added to the tower house to form what one would typically think of as a castle. An example is shown above, in the graphic of Castle Campbell. The original tower house lies to the right. A defensive wall forming a courtyard extends to the left. The east range, or wing, was added later and forms part of the wall seen directly in the center of the graphic. 
   Later, the designation of castle was given to manors and estate houses, both large and small. Two examples are Inveraray Castle, home of MacCailein Mor, Chief of Clan Campbell, and Culzean Castle, previously home to the Kennedy chief and now in the hands of the National Trust for Scotland. In both cases, the buildings are more palatial homes than castles.