The Prague Castle, Prague, Czech Republic
Prague Castleis a castle in Prague where the Czech kings, Holy Roman Emperors and presidents of Czechoslovakia and the Czech Republic have had their offices. The Czech 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 meters in length and an average of about 130 meters wide.
References sources : wikipedia