Longyou Caves

The Longyou Caves, also called the Xiaonanhai Stone Chambers , are a group of 24 artificial sandstone caverns located at Fenghuang Hill, near the village of Shiyan Beicun on the Qu River in Longyou County, Quzhou prefecture, Zhejiang province, China. It is unknown when the caves were created; they are mentioned in a 17th century poem by the Yu Xun, and clay from pots dated to between 206BC and 23 AD was found in silt within the caves.

Discovery
In June 1992, four farmers in Longyou found the caves when they drained the water of five small ponds in their village. The ponds turned out to be five large manmade caverns. Further investigation revealed 19 more caverns nearby. They have been determined to be more than 2000 years old and their construction is not recorded in any historical documents.

About 200 km to the northwest, the Huashan Grottoes at the riverbanks of the Xin'an River somewhat resemble the Longyou Caves but are likely to have been built more than 1,500 years later during the late Ming Dynasty (1552–1667 AD).

Description
The caves are notable in several respects:
 * The caves are very large considering their man-made origin: the average floor area of each cave is over 1000 sqm, with heights of up to 30 m, and the total area covered is in excess of 30000 sqm.
 * The ceiling, wall and pillar surfaces are all finished in the same manner, as a series of parallel bands or courses about 60 cm wide containing parallel chiselling marks set at an angle of about 60° to the axis of the course.
 * They have maintained their structural integrity and do not interconnect with each other.