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. The cave extends some 50 metres into the cliff at the surface, and is about 150 metres (490 ft) deep, with a sandy bottom.(source: Wikipedia)