The Fun Fun Cave is a cavern system reaching more than 28 kilometers long, located on a karstic or limestone hill on the southeast of Hato Mayor.
Its formation began more than 20 million years ago. Its limestone or calcareous type rocks, originated by the remains of marine coral shells and other organic lifeform, are composed of calcium carbonate and sodium. This composition allows water to dissolve them and form the cavern, in a continuous process that takes millions of years.
The Almirante River travels through 7 kilometers of the cave and the rise of its waters has shaped the magical underground tunnels and corridors. Drops of rainwater break through the rock to form stalactites, stalagmites, flowstones, daylight holes and columns, creating underground landscapes of singular beauty.
The cavern is home to fish, shrimp, insects, bats and birds. Fish and shrimp lack pigmentation and eyesight due to lack of sunlight, and possess high sensitivity as a defense mechanism.
Insects develop large antennae, tentacle-like, which serve as remote sensors to detect danger.
Bats that predominate inside the Fun Fun Cave feed on fruits.
Birds that inhabit the cavern are migratory and correspond to species of swallows that nest during the winter, building their nests in the vicinity of the entrance.