The Grand Staircase (also called the Marble Staircase) is a massive structure in Hogwarts which is located in the Grand Staircase Tower. It is mainly used to access each floor in the castle, including the Basement andDungeons. There are hundreds of portraits on the walls of the Grand Staircase Tower. Some of the portraits reveal hidden/secret passageways within the school. The multiple staircases move from one platform to another in a sequence that ends at the seventh floor. The moving staircases came from an idea by Rowena Ravenclaw, who was one of the founders of Hogwarts.