What island did king john think the Caribbean island were apart of?

King John of England mistakenly believed that the Caribbean islands were part of the mythical island of "Antillia," often referred to as the "Isle of Seven Cities." This legend suggested that Antillia was a large island located in the Atlantic Ocean, which many European explorers sought after during the Age of Discovery. The confusion arose from the limited geographical knowledge of the time and the blending of myths with actual discoveries.