Millbank Prison Blue Plaque

You are standing near a massive, cylindrical granite block that marks the former location of Millbank Prison. This site was once occupied by a sprawling, six-petalled fortress that served as Britain's National Penitentiary from 1816 until 1890. Its design was so complex and labyrinthine that prison guards famously invented a code of chalked symbols on the walls just to navigate the three miles of cold, gloomy corridors without getting lost.