China's immense Miao Room cavern, hidden beneath rolling hills and reachable only by an underground stream, is the world's biggest cave chamber, an international mapping team reported on Sunday. (Related: "China's Supercave.")

A laser-mapping expedition funded by the National Geographic Society reported the new measurement at the United Kingdom's national caving conference in Leek this weekend.

Richard "Roo" Walters, a British co-leader of the 2013 international caving expedition conducted under the auspices of China's Institute of Karst Geology in Guilin, reported that the Miao Room Chamber measures some 380.7 million cubic feet (10.78 million cubic meters) in volume. (See: "Empire of Rock" in National Geographic Magazine.)

"To me this is like discovering that K2 is larger than Everest!" said