Prague, Czech Republic - Castle : is the largest ancient castle in the world. And, it is a castle 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 within a hidden room inside it.
Windsor Castle, Berkshire England. The original castle was built in the 11th century after the Norman invasion by William the Conqueror. Since the time of King Henry I, it has been used by succeeding monarchs and is the longest-occupied palace in Europe. #jjexplores