Strap on a miners hat and gloves and get ready to explore the underbelly of the world's largest active volcano. Tours through these fascinating caves and lava tubes underneath the volcano must be arranged in advance, but are well worth a little extra planning. Located off Highway 11 between Hilo and Volcanoes National Park, the Caverns are comprised of four main tubes, each 500-700 years old and full of stalactites, stalagmites, and a variety of different colored flowstone. The largest lava tube in the world is here -- 40 mi long, it has 80-foot ceilings and is 80 feet wide. Tours can range from safe and easy (safe enough for children five years old and up) to long and adventurous. For those not so sure about "spelunking," an easy walking tour through the lava tube can also be arranged. www.kilaueacavernsoffire.com. Open by appointment only.