The castles in the Loire Valley are an easy day-trip out of Paris. To say that Château de Chambord is enormous just does not cover it. Consider that it has 426 rooms, 80 staircases, 282 fireplaces, a double-helix staircase, a moat, a flamboyant roof (originally designed to look like the skyline of Constantinople) all of which is surrounded by a wall 32km long. The estate is the same area as Inner Paris... Well, you get the idea. It is at least ten times larger than enormous.
During WWII, Chambord was used to store art from French museums including the Louvre. As many as 5000 crates were protected here, one of which contained the Mona Lisa. You can read much more here and here.
Built in th 16th Century as a hunting lodge, it was rarely inhabited, drafty, and bitter cold in the winter.