Coming to Capri? Make sure you visit the Blue Grotto and take the tour around the island by boat! Inside the Blue Grotto of Capri.

The Blue Grotto (Italian: Grotta Azzurra) is a sea cave on the coast of the island of Capri, southern Italy. Sunlight, passing through an underwater cavity and shining through the seawater, creates a blue reflection that illuminates the cavern. [Wikipedia]