Situated in the 1580-sq-km wilderness of Phu Hin Bun National Protected Area , this 7.5km river tunnel, running beneath an immense limestone mountain, ratchets up the fear dial like some natural gothic ghost ride. Puttering into its 100m church-high darkness by longtail is the only way to travel, your stomach turning as the cave entrance becomes a pinpoint of light. Halfway, you'll moor up and stroll through a dramatically lit stalactite wood, like an abandoned old Star Trek set.
Remember to bring a decent torch, plus rubber sandals. Kong Lo village (about 1km downstream of the cave mouth) is your base for this unforgettable trip. Takes around two hours for the return trip with a 20-minute drinks break at a sala on the other side of the cave. Lifejackets are handed out at the ticket office.
