Windsor Castle, in Windsor in the English county of Berkshire, is the largest inhabited castle in the world and, dating back to the time of William the Conqueror, is the oldest in continuous occupation. The castle's floor area is approximately 45,000 square metres (about 484,000 square feet).Together with Buckingham Palace in London and Holyrood Palace in Edinburgh, it is one of the principal official residences of the British monarch. Queen Elizabeth II spends many weekends of the year at the castle, using it for both state and private entertaining. Her other two residences, Sandringham House and Balmoral Castle, are the Royal Family's private homes.