Just as towers and crenellations indicated a building's status, so the crenellated wall signified a castle in the visual arts and in that distinctive medieval sign language known as heraldry. The heraldic symbol of the kingdom of Castile, for example, consisted of a wall and three crenellated towers. This simple composition was easily recognized and reproduced.
Ch. 4 : The Castle as Symbol and Palace - Medieval castles (2005)