The biggest house in the world is Windsor Castle belongs to royalty, as you might have guessed. Windsor Castle is considered the biggest house in the world because it is actively inhabited. The biggest castle no longer dwelled in is Prague Castle in the Czech Republic., located in England, Berkshire, with a surface of around 484,000 square feet (about 45,000 square meters). Having its structure changed over the centuries, the castle now occupies 13 acres of land, having 1,000 rooms. Along with Buckingham Palace in London and Holyrood Palace in Edinburgh, Windsor Castle is one of the principal official residences of the British monarch. The resident is Queen Elizabeth II that made the castle her home beginning with 1952.