Inside Son Doong (via Oxalis)

No one had seen anything like Son Doong cave until 1991, when a man named Ho Khanh happened upon its entrance in the Vietnam jungle. Due to the sound of a roaring river and the sheer drop into the darkness, the interior of the cave wasn’t glimpsed by human eyes until 2009 on a British Cave Research Association expedition. What they found was a cave that was not just five times larger than the previous largest cave in Vietnam, but twice as massive as Deer Cave in Malaysia, the record holder for world’s largest cave.

Rappelling into the cave (via Oxalis)

Now, tours for the public are being organized for the first time through operator Oxalis. The first adventurers spent nearly a week journeying to Son Doong and camping inside the cave in August, and the plan is for the tours to be held annually between February and August. The cave is 5.5 miles long, and includes a whole roaring river, stalagmites that tower up to 260 feet, geological formations that look like surreal land art, wide sinkholes, rare rock structures called cave pearls, fossils as old as 300 million years, and even a jungle with trees growing to nearly 100 feet where flying foxes, monkeys, and hornbills roam.

Camping in the cave (via Oxalis)

The jungle and some other parts of the cave are open to the sky due to a collapse at one point in its formation over the course of two to five million years. Preservation of the cave is an essential component of the tours, which will be kept small, and are run with the approval of the local Quang Binh Province government.

Inside the cave (via Oxalis)

All visits to the cave have to start with an about 250-foot rappel into the darkness, but for those willing to take on the descent (and pay $3,000), the chance is now yours. More details and photographs can be found on Oxalis’ website.

Here’s National Geographic’s documentary on “Vietnam’s Infinite Cave”:

WORLD’S LARGEST CAVE: HANG SON SOONG, Vietnam