Miao Room

Miao Room is the largest known cave chamber by volume in the world. It is a part of the Gebihe cave system, which is located in Ziyun Getu He National Park, in Ziyun county of the Chinese province of Guizhou.
The chamber, discovered by a French expedition called Gebihe'89 in 1989, measures in length, in width, has an area of and a volume of . In 2013 members of a British led expedition measured the chamber using 3-D laser scanners.
Geology and formation.
For more than 600 million years the area, in which the Gebihe cave system is located, was covered by sea and during this time it accumulated miles-thick layers of sediments, including limestone. The uplift of the area and then the erosion of the limestone layer created today's massive cavern system.
The system spreads out in limestones and dolomite of Carboniferous and Permian age. Old cave levels have been cut by erosion and follow the base level lowering caused by Tertiary uplift.