The Round Tower is the central keep of Windsor. It has been on the site in one form or another since the 1100’s when it was made of wood. William the Conqueror is responsible for starting construction on the tower and the castle itself. Along with the Tower of London, William needed Windsor to keep the conquered Saxons in check. The castle has never fallen, although in its history it has seen numerous sieges including one in the early 1200’s when King John’s barons rose against him and eventually forced the Magna Carta issue.