Grotta Azzurra (Blue Grotto) is located in Italy
The Blue Grotto (Italian: Grotta Azzurra) is a sea cave on the coast of the island of Capri, southern Italy. Sunlight passes through an underwater cavity and shines through the seawater, creates a blue reflection that illuminates the cavern. The water in the cave appears more light-filled than the air; a visitor who places a hand in the water can see it glow eerily silver in this light.
Submitted by Jennifer Luo. More information about this location can be found here.