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.)

View Images SOURCES: Andy Eavis, Tim Allen, Richard Walters, Peter Smart, Daniela Pani, Jane Allen, AND Mark RichardsoN, China Caves Project; Zhang hai, INSTITUTE OF KARST GEOLOGY, GUILIN, CHINA, CREDIT: Martin Gamache and Lauren James, NG Staff; Juan Velasco

"To me this is like discovering that K2 is larger than Everest!" said Tim Allen, an expedition co-leader, in an email. The Miao Room volume measurement exceeds Sarawak Chamber in Malaysia, the past title-holder, by about 10 percent. But the Malaysian cavern is still the world’s largest by surface area, with some 1.66 million square feet (154,500 square meters) of expanse.

View Images SOURCES: Andy Eavis, Tim Allen, Richard Walters, Peter Smart, Daniela Pani, Jane Allen, AND Mark RichardsoN, China Caves Project; Zhang hai, INSTITUTE OF KARST GEOLOGY, GUILIN, CHINA, CREDIT: Martin Gamache and Lauren James, NG Staff; Juan Velasco

Sizing Up a Supercave

The expedition first mapped the chamber with extensive laser scanning surveys in 2013. To make the new size estimate, the team reprocessed the results with experts from the U.K.'s University of Lancaster to yield more precise measurements of the cavern.

The team also presented new laser scanning measurements of two other large cave chambers in southern China, Titan Chamber and Hong Meigui Chamber, as well as the Sarawak Chamber, at the meeting.