Hawaii has the longest lava tube in the world. It’s in this guy’s backyard.

Dave Bunnell / Under Earth Images/Wiki CommonsA world of caves exists beneath Hawaii’s surface that’s still relatively unknown. But the most distinguished is on the east side of the island in the district of Puna, where Kazumura Cave can be found. Kazumura Cave is the longest lava cave in the world. Lava once flowed through this ancient tube system that was active during the Ailaau eruption in the 15th century. Dave Bunnell / Under Earth Images/Wiki CommonsToday, the extensive cave system lies beneath hundreds of properties.