Exploring the world's largest cave

Cave Jungle The roof of Son Doong collapsed centuries ago. The sunlight and fresh air allowed a lush jungle to take root inside the cave. Here, an Australian named Ben Mitchell marvels at the landscape. (Simon Dunne/Oxalis Tours)

Plant Life in Cave The giant cave contains two "daylight windows," which allow light to enter many parts of the cave. At the base of these windows are large jungles which use all the available light to nourish trees that grow almost 10 stories tall. (Ryan Deboodt/Oxalis Tours)

Stunning Stone Giant stalagmites over 250 feet high and enormous rimstone pools are present throughout the cave. (Adam Spillane/Oxalis Tours)

Hope and Vision Passage A half-mile block of 40-story buildings could fit inside the largest part of the cave, which may be the world's biggest subterranean passage. (Howard Limbert/Oxalis tours)

Fall Floods From September to January is flooding season in the region, so there are no tours while the cave weathers the rainy season. (Ryan DeBoodt/Oxalis Tours)

Sleeping Among the Stalagmites On their first night inside the cave, visitors camp near Hand of Dog, a massive stalagmite that looks like a dog's paw. (Ryan Deboodt/Oxalis Tours)

River Cave An entire river runs inside the cave. Scientists have discovered never-before-seen plant species around Son Doong's waterfalls. (Ryan Deboodt/Oxalis Tours)

Cave Pearls Rare cave pearls fill dried-out terrace pools inside Son Doong. They formed drip by drip over the centuries as calcite crystals left behind by water layered themselves around grains of sand. (Ryan Deboodt/Oxalis Tours)

Conquering an Infinite Drop The man who discovered Son Doong never fully entered the cave because he feared its steep drop into what appeared to be an abyss. Next year, <a target="_blank" href="http://www.oxalis.com.vn/son-doong-cave#">Oxalis Tours</a> will take every visitor down a nearly 300-foot drop into the cave's entrance. (Ryan Deboodt/Oxalis)