After their reunion fails to lives up to Queen Ginevra’s hopes and dreams, she storms off into her castle, which incidentally rotates by means of steam powered by the volcanoes, and literally moments later the steam goes berserk because the volcanoes start erupting and Queen Ginevra gets spun to death.

The rotating castle is straight out of Preiddeu Annwfn—Caer Sidi—and it has been long enough since I read the book that I can't remember if it's called out by name, but years later it randomly occurred to me and I was duly mind blown.