It is rather difficult to determine the biggest chamber. First its a problem how to measure its dimensions, and then its a problem to decide which aspect of the survey data is most significant.
How do you measure the size of an underground chamber? In caves it is rather difficult to determine exact volumes, as surveying just follows a single line. You just get a sort of skeleton of the cave. The solution to measure surface and volume is to add the distance to walls, floor and ceiling. You measure to the wall as often as possible. In big chambers you may survey once along the wall. The height is determined using a thin rope and a gas filled balloon. This is also done as often as possible. The result is nevertheless very inaccurate concerning volume, but length and width are quite accurate.
As a result it is actually impossible to make a sort of ranking based on survey data. While volume would be the best criteria for this, it is also the least accurate number. This changed in recent years with the introduction of 3-D laser scanners. They allow the scan of all walls and ceiling and the construction of a computer model. Unfortunately the technology is very expensive and the survey is a lot of work. While currently only a dozen caves was scanned this might become the main surveying technique for such huge caverns in a few years.
|641m||429m||113m||154,530m²||9,670,000m³||Sarawak Chamber in Good Luck Cave, Gunung Mulu National Park, Sarawak, Malaysia.||This is the biggest cavern (biggest single chamber) of the world. It is 700 m long and 70 m high with an average width of 300 m.|
|824m||336m||177m||140,540m²||10,570,000m³||Miaos Room in the Gebihe system in China||This chamber was discovered in 1989 by a French expedition and in 2013 a British expedition measured the chamber using 3-D laser scanners. It is probably the biggest underground chamber by volume, but it is definitely the biggest of those measured by 3-D laser scanners.|