I'm thinking that water eroded a pocket 200' down. As it eroded, the ceiling started to collapse bit-by-bit. As this process continued, the ceiling continued to collapse a bit at a time until it reached the surface. Erosion of this type where the point of erosion is at depth can create symmetric, columnar holes or depressions, although it depends a lot on soil type.
Are there any reasonable explanations for spectacular sinkholes in China? After the spectacular picture of a sinkhole in Guatemala caused by tropical storm Agatha, the Chinese internet has been abuzz with reports of large numbers of the eerily circular formations suddenly appearing across China. ...