The Khao Mai Kaeo caves, hidden in the middle of Ko Lanta, are accessible from Ao Khlong Nin. Entry to these caves is via a narrow opening dug out of the rock. Once inside, several chambers follow on one from the other (some populated by bats) and cathedral-like rooms adorned with stalagmites and stalactites alternate with low-ceilinged passageways. Visitors will even discover a small underground lake here where it's possible to swim.