Photographs from a National Geographic caving expedition in Vietnam’s Phong Nha-Ke Bang National Park.

HANG SON DOONG, or “mountain river cave,” is 2.5 miles long with a max width of 300ft and a max height of 600ft, making it the largest cave passage in the world. Exploration of Hang Son Doong and the surrounding system began in 2009, and a year later National Geographic writer Mark Jenkins and photographer Carsten Peter accompanied the mapping team on its second visit. The story and photos of the expedition appear in the January issue of the National Geographic magazine, and Matador Trips was lucky enough to be granted permission to share some of the images here. Make sure to check out the full gallery.

1

Phong Nha-Ke Bang National Park, Vietnam

From National Geographic: Mist sweeps past the hills of Phong Nha-Ke Bang National Park, its 330 square miles set aside in 2001 to protect one of Asia's largest cave systems. During the Vietnam War, North Vietnamese soldiers hid in caves from U.S. air strikes. Bomb craters now serve as fishponds.Photo: Carsten Peter/National Geographic

2

Cave skylight and giant passage

From National Geographic: Like a castle on a knoll, a rock formation shines beneath a skylight in Hang Son Doong. A storm had just filled the pool, signaling that exploring season was coming to an end.Behind the scenes with Mark Jenkins: "I always tried to put my tent up underneath the giant skylights, so I could get at least a little sunshine every day."Photo: Carsten Peter/National Geographic

3

Cave columns and pools

From National Geographic: A giant cave column swagged in flowstone towers over explorers swimming through the depths of Hang Ken, one of 20 new caves discovered last year in Vietnam.Behind the scenes with Mark Jenkins: "The hardcore Yorkshire cavers plunged deep into the darkness to set up their camp!"Photo: Carsten Peter/National Geographic

4

Hang Ken cavern

From National Geographic: In the dry season, from November to April, a caver can safely explore Hang Ken, with its shallow pools. Come the monsoon, the underground river swells and floods the passages, making the cave impassable.Behind the scenes with Mark Jenkins: "I also camped with the Vietnamese porters, and in the morning they would catch swallows mating on the wing (dropping through the skylights stacked atop one another), kill them, and barbecue them over the campfire."Photo: Carsten Peter/National Geographic

5

Caver in a shaft of light

From National Geographic: A climber ascends a shaft of light in Loong Con, where humidity rises into cool air and forms clouds inside the cave.Behind the scenes with Mark Jenkins: "Hardcore cavers are a breed unto themselves, with the same passion and drive as climbers, and yet the actual experience is the exact opposite: climbers ascend toward the sun and sky, cavers descend toward darkness and ever smaller holes."Photo: Carsten Peter/National Geographic

6

Navigating the cave pools

From National Geographic: Navigating an algae-skinned maze, expedition organizers Deb and Howard Limbert lead the way across a sculpted cavescape in Hang Son Doong. Ribs form as calcite-rich water overflows pools.Behind the scenes with Mark Jenkins: "The great fear in climbing is exposure, the great fear in caving is claustrophobia (of course many climbers do not experience exposure and many cavers don't experience claustrophobia)."Photo: Carsten Peter/National Geographic

7

January 2011 National Geographic cover

Cover of the January 2011 issue of the National Geographic magazine (on newsstands now), in which you can read about the mapping of this cave system and see more incredible images from the expedition.