This grand room is where Hearst's guests assembled before going to dinner. Hearst not only owned enough tapestries to drape around the top of the walls, but he also had more in storage. So he could change them when he wanted to, the ceiling can be raised or lowered to accommodate their size. The tour group you see in the picture is walking into the dining room.
The "secret" door that Hearst used to enter this room is part of the wood paneling, just past where the people are walking past the dining room door.