Hongs are one of the most remarkable of Mother Nature's creations. They started out as karst mountains with caves inside, caves eroded by water till rivers flowed inside. They existed for eons inhabited only by bats and long ago by cavemen. Eventually the tops of the mountains fell in exposing the caves to the sun. Fertilized by the rich soil a new world grew. Unlike anywhere else on Earth, it can best be described as something from the time of dinosaurs. Beyond beauty, these Hongs, once seen, will never leave your memory. You owe it to yourself to visit them if you are ever in Thailand.