9. Blue Grotto (Italy)
You can find this remarkable sea cave on the island of Capri; if you visit the Blue Grotto during the day, you can catch rays of sunlight passing through the underwater cavity, creating a spectacular reflection that lights up the entire cave.
Fun Fact: As the entrance to the cave is relatively small, visitors can only access it by rowboat. Furthermore, tours are only organised if weather conditions are favourable.
