Eleven-year-old Christian and seven-year-old Zack love everything about medieval times. Their mom and dad want them to have a room all their own that they'll hopefully still love when they're teenagers. Designer Grace D. Knowlton's is up to the challenge of incorporating a medieval theme in an inviting play space. Her ambitious design includes a reading cave, secret tunnels, faux rock walls, an armory, a lounge area with a flat-screen TV and a giant, hand-painted mural of a mythical land.