sea cave, Malta - Sea caves or the Blue Grotto are located on the island of Filfla in Malta. These caves are popular for their beauty and their location when combined with the sunrise, leads to beautiful shades of blue in the water.
Explore the ancient caves of Hang Son Doong, Vietnam. Hang Son Doong is one of the largest caves in the world and features a fast-flowing underground river. For spelunkers, exploring Hang Son Doong is the equivalent of scaling Mount Everest.