The Big Island is one of the best places on Earth to explore the underworld. With intense volcanic activity occurring over millions of years, there are hundreds of underground lava tubes, caves, and volcanic formations to explore and enjoy, making Hawaii’s largest island the perfect destination for those who love to hike and spelunk through the depths of the world. Along the Big Island’s eastern side is one of the largest and most extensive underground lava formations in the world in Kaumana Cave. Over 25 miles long and well-maintained, it’s one of the best places on the Big Island to explore caves with the whole family. Cool during the summer heat and a dry respite from Hilo’s famous rainfall, the cave has concrete access stairs and walkways that make for a quick, easy trip through the lit areas of the cave. Most visitors spend about 20 minutes exploring the best-lit section before heading on to their next activity, but those more adventurous are welcome to strap on a flashlight or headlamp and explore nearly 2 more miles of easily accessible, but unique underground areas. For extreme spelunkers, you’ll need to plan ahead to explore even more of Kaumana. Because the cave terminates onto private land, you’ll need to get permission from the landowners to complete the tour and sign a waiver before going deeper. You’ll also need to bring a hard hat, water, and at least three sources of light. Formed after a significant lava flow from Mauna Loa threatened the city of Hilo in 1881, Kaumana is one of the best destinations to learn and witness the impact of volcanic activity and how these lava flows can destroy as well as create. If you’re a cave junkie and are planning a visit to the Big Island, you won’t want to miss Kaumana Cave.