October 20, 2008–A cave explorer stands before an imposing stalagmite–made of mineral deposits–near an entrance to the Xe Bang Fai River cave in central Laos.
An expedition in February 2008, co-led by veteran caver John Pollack, comprehensively mapped and photographed the 5.9-mile (9.5-kilometer) length of the little-known cavern for the first time.
The spelunking team encountered some of the largest rooms and most impressive structures of any river cave on Earth, Pollack said.
A river cave is any cave with an active water source flowing through it.
Everything about the cave is big–from its towering entrances to its phobia-inducing spiders, which can be 10 inches (25 centimeters) across, Pollack added.
"It's also extremely well decorated with spectacular formations," Pollack said
PHOTOS: Gigantic River Cave Revealed in Laos