The Blue Grotto (Grotta Azzurra) is a noted sea cave on the coast of the island of Capri, Italy. Sunlight, passing through an underwater cavity and shining through the seawater, creates a blue reflection that illuminates the cavern.
From TripAdvisor: "Aragonese Castle - Ischia, Italy. Ischia's our favorite place to travel in the world! No cruise ships, no designer boutiques, only fishing villages that have turned into resort towns.