People will rightly rave about Versailles, but don’t forget about Fontainebleau! Originally a fortified keep dating to the 1100s, it was largely rebuilt in grand Renaissance style by François I starting in the 1520s. Later monarchs—Henri IV, Louis XIV, Napoleons I and III—made their mark on it in various ways.
It’s a massive, sprawling castle with any number of wings jutting out hither and yon. Only a small fraction of it was open to the public and we only got to enjoy some of that, because we got there too late in the afternoon.
Like Chambord, Fontainebleau was very popular with kings as a hunting castle, and is surrounded by a forest that’s now a nature preserve.