Prague Castle (Czech: Pražský hrad) is a castle in Prague where the Kings of Bohemia, Holy Roman Emperors and presidents of Czechoslovakia and the Czech Republic have had their offices. The Bohemian Crown Jewels are kept here. Prague Castle is one of the biggest castles in the world (according to Guinness Book of Records the biggest ancient castle) at about 570 metres in length and an average of about 130 metres wide.