Who's afraid of the dark? Test yourself at the end of this underground walk by switching off your flashlight. Eerie! One of the odder sights on the Road to Hana, this mammoth cave was formed by ancient lava flows some 960 years ago. It once served as a slaughterhouse – 17,000lb of cow bones had to be removed before it was opened to visitors. It's the 18th largest lava tube in the world and the largest by far on Maui.
Winding your way through the extensive cave, which reaches heights of up to 40ft, you’ll find a unique ecosystem of dripping stalactites and stalagmites. You might see signs reading 'Nuclear Fallout Shelter,' but it's no longer needed for this purpose and can only sustain 15 people for six weeks anyway – the owner has stockpiled enough food for himself and 14 others. The journey is well signed, takes about 45 minutes, and is a perfect rainy-day activity. Admission includes flashlights and hard hats. If you want to lose the kids, an adjoining botanical maze made from red ti plants is no extra charge beyond the ticket price. Hana Lava Tube is half a mile from the Hana Hwy.