青の洞窟 (Aoi no Dōkutsu), or the Blue Cave, is a famous sea cave located on the island of Capri in Italy. It is renowned for its stunning blue waters, which are illuminated by sunlight filtering through an underwater opening. Visitors can take small boats to enter the cave and experience its mesmerizing colors. The cave is approximately 60 meters long and 25 meters wide, with a height of about 15 meters. The best time to visit is during midday when the sunlight creates the most vibrant blue effect. The Blue Cave is a popular tourist attraction, drawing visitors from around the world.