An Imperial staircase (sometimes erroneously known as a "double staircase") is the name given to a staircase with divided flights. Usually the first flight rises to a half-landing and then divides into two symmetrical flights both rising with an equal number of steps and turns to the next floor. The feature is reputed to have first been used at El Escorial. The Jordan Staircase of the Winter Palace is a notable example, while other such staircases can be found at Buckingham Palace, Windsor Castle, Palazzo Reale di Caserta, Palacio Real de Madrid and Mentmore Towers.