{"it":{"id":"CHN-LON","kind":"site","sub":"Asia","name":"Longyou Caves","place":"China","lat":29.062,"lon":119.184,"date":"see measurements","mat":"Cretaceous pelitic siltstone (Quxian Fm)","nfacts":14,"tags":["Asia"],"sum":"In 1992 villagers in Zhejiang, China, pumped the water out of a few ponds and found a hall of rock beneath. It was the first of 24 large caverns cut by hand into Fenghuang Hill.","why":"24 hand-cut caverns under a Chinese village, and no record of who made them or why.","src":[414],"nsrc":2,"yt":"Why carve caverns this large and leave no record of the work?","rel":["LEV-001","ASI-007"],"hook":"Near Longyou, China, 24 hand-cut caverns lay hidden under water until 1992."},"S":{"414":["Wikipedia: Longyou Caves","https://en.wikipedia.org/wiki/Longyou_Caves"]},"rec":{"id":"CHN-LON","alias":[],"ms":[{"f":"caverns","a":"count","v":"24 (5 large + 19 others)","u":"count","o":"","unc":"","by":"Li et al. 2009","yr":"2009","m":"as stated","c":"Li et al. 2009","pg":"","url":"https://doi.org/10.1016/j.tust.2008.08.003","b":"S","bb":"","t":"MEASUREMENT","n":"","id":"M2824"},{"f":"caverns","a":"elevation (range)","v":"39-69","u":"m","o":"","unc":"","by":"Li et al. 2009","yr":"2009","m":"as stated","c":"Li et al. 2009","pg":"","url":"https://doi.org/10.1016/j.tust.2008.08.003","b":"S","bb":"","t":"MEASUREMENT","n":"","id":"M2825"},{"f":"caverns","a":"span","v":"18-34","u":"m","o":"","unc":"","by":"Li et al. 2009","yr":"2009","m":"as stated","c":"Li et al. 2009","pg":"","url":"https://doi.org/10.1016/j.tust.2008.08.003","b":"S","bb":"","t":"MEASUREMENT","n":"","id":"M2826"},{"f":"caverns","a":"height","v":"8-18","u":"m","o":"","unc":"","by":"Li et al. 2009","yr":"2009","m":"as stated","c":"Li et al. 2009","pg":"","url":"https://doi.org/10.1016/j.tust.2008.08.003","b":"S","bb":"","t":"MEASUREMENT","n":"DISAGREES with Wikipedia ceilings up to 30 m","id":"M2827"},{"f":"caverns","a":"height (max)","v":"~30","u":"m","o":"","unc":"","by":"Wikipedia","yr":"","m":"as stated","c":"Wikipedia","pg":"","url":"https://en.wikipedia.org/wiki/Longyou_Caves","b":"S","bb":"","t":"MEASUREMENT","n":"DISAGREES with Li 2009","id":"M2828"},{"f":"caverns","a":"roof thickness","v":"0.6-20","u":"m","o":"","unc":"","by":"Li et al. 2009","yr":"2009","m":"as stated","c":"Li et al. 2009","pg":"","url":"https://doi.org/10.1016/j.tust.2008.08.003","b":"S","bb":"","t":"MEASUREMENT","n":"","id":"M2829"},{"f":"host rock","a":"rock type","v":"Cretaceous pelitic siltstone (Quxian Formation)","u":"text","o":"","unc":"","by":"Li et al. 2009","yr":"2009","m":"as stated","c":"Li et al. 2009","pg":"","url":"https://doi.org/10.1016/j.tust.2008.08.003","b":"S","bb":"","t":"MEASUREMENT","n":"","id":"M2830"},{"f":"location","a":"distance from Longyou town","v":"3 km N, Fenghuang Hill","u":"km","o":"","unc":"","by":"Li et al. 2009","yr":"2009","m":"as stated","c":"Li et al. 2009","pg":"","url":"https://doi.org/10.1016/j.tust.2008.08.003","b":"S","bb":"","t":"MEASUREMENT","n":"","id":"M2831"},{"f":"each cave","a":"floor area (average)","v":">1000","u":"m2","o":"","unc":"","by":"Wikipedia","yr":"","m":"as stated","c":"Wikipedia","pg":"","url":"https://en.wikipedia.org/wiki/Longyou_Caves","b":"S","bb":"","t":"MEASUREMENT","n":"","id":"M2832"},{"f":"all caves","a":"floor area (total)","v":">30000","u":"m2","o":"","unc":"","by":"Wikipedia","yr":"","m":"as stated","c":"Wikipedia","pg":"","url":"https://en.wikipedia.org/wiki/Longyou_Caves","b":"S","bb":"","t":"MEASUREMENT","n":"","id":"M2833"},{"f":"walls","a":"tool marks","v":"parallel chisel bands ~60 cm wide at ~60 deg","u":"text","o":"","unc":"","by":"Wikipedia","yr":"","m":"as stated","c":"Wikipedia","pg":"","url":"https://en.wikipedia.org/wiki/Longyou_Caves","b":"S","bb":"","t":"MEASUREMENT","n":"","id":"M2834"},{"f":"discovery","a":"history","v":"found 1992 when villagers pumped out ponds","u":"text","o":"","unc":"","by":"Li et al. 2009 / Wikipedia","yr":"2009","m":"as stated","c":"Li et al. 2009 / Wikipedia","pg":"","url":"https://doi.org/10.1016/j.tust.2008.08.003","b":"S","bb":"","t":"MEASUREMENT","n":"","id":"M2835"},{"f":"caverns","a":"dating (relics)","v":">=2000 years","u":"","o":"","unc":"","by":"Li et al. 2009","yr":"2009","m":"derived","c":"Li et al. 2009","pg":"","url":"https://doi.org/10.1016/j.tust.2008.08.003","b":"S","bb":"","t":"INTERPRETATION","n":"INTERPRETATION from relics; no direct date of excavation","id":"M2836"},{"f":"silt fill pottery","a":"dating (typology)","v":"206 BC-AD 23 (Han)","u":"","o":"","unc":"","by":"Wikipedia","yr":"","m":"derived","c":"Wikipedia","pg":"","url":"https://en.wikipedia.org/wiki/Longyou_Caves","b":"S","bb":"","t":"INTERPRETATION","n":"INTERPRETATION; dates fill, not cutting","id":"M2837"}],"lab":[],"eng":[],"ori":[],"gaps":[{"a":"largest_block","r":"not found in free sources reached"},{"a":"block_mass","r":"not found in free sources reached"},{"a":"slope_face_angle","r":"no published face/slope angle in sources reached (often n/a for non-pyramidal sites)"},{"a":"wall_batter","r":"no published batter survey in free sources"},{"a":"orientation","r":"no published azimuth reached"},{"a":"corner_precision","r":"no published precision survey in free sources"},{"a":"levelness","r":"no published levelling survey in free sources"},{"a":"geochem_petro","r":"not found in free sources reached"},{"a":"quarry_source","r":"not found in free sources reached"},{"a":"mortar","r":"dry-stone construction or no binder analysis in free sources"},{"a":"volume_labor","r":"no volume/labour estimate in sources opened"},{"a":"construction_phases","r":"no phase sequence in sources opened"},{"a":"lab_date_material","r":"no lab date with dated material in sources opened"},{"a":"hydrology_acoustics","r":"no published hydrology/acoustic measurement in sources opened"},{"a":"magnetic_radiation","r":"no published magnetic/radiation survey found (searched site name + magnetometry/radiation; Wikipedia, Google Scholar snippets)"},{"a":"metals_clamps","r":"no metal/clamp evidence reported in sources opened"}],"dat":[],"aa":[{"id":"AA025","a":"undocumented vast caverns","who":"popular web/forums (no named author located)","main":"Qin/Han quarrying; purpose unknown","ms":"https://doi.org/10.1016/j.tust.2008.08.003","st":"unresolved","n":"excavation physically ordinary; purpose and date undocumented","nl":8}],"ac":[{"v":"enormous caverns with no historical record imply unknown builders/technology","who":"popular web/forums (no named author located)","url":"","b":"I","ce":"excavation in soft siltstone, chisel bands visible; Han pottery in fill"}],"me":[{"v":"Qin/Han-era quarrying or storage; purpose undocumented","ev":"Li et al. 2009 geotechnical survey","s":"https://doi.org/10.1016/j.tust.2008.08.003"}],"ci":[],"cq":[],"sd":[],"sub":[],"site":{"age":"see measurements","dm":"","lab":"NO","weak":"","unesco":"","dens":"STUB"},"co":{"lat":"29.06160","lon":"119.18400","src":"Wikidata P625 (Q16894311)","agree":"agree","b":"V","note":"Wikidata vs OSM delta 0.0006 deg (~0.06 km)","osm":"https://www.openstreetmap.org/way/893716464"},"src":[{"id":null,"t":"Li et al. 2009","u":"https://doi.org/10.1016/j.tust.2008.08.003"},{"id":null,"t":"Wikipedia","u":"https://en.wikipedia.org/wiki/Longyou_Caves"},{"id":"VCHN-LON-3","t":"Journal article, DOI 10.3724/SP.J.1235.2011.00131","u":"https://doi.org/10.3724/sp.j.1235.2011.00131"},{"id":"VCHN-LON-4","t":"Chinese Journal of Rock Mechanics and Engineering 24(12), 2005: deformation and reinforcement of ancient caves","u":"https://rockmech.whrsm.ac.cn/EN/Y2005/V24/I12/2018"},{"id":"VCHN-LON-5","t":"Institute of Geology and Geophysics, CAS: engineering geology of the Longyou Grottoes (archived)","u":"https://web.archive.org/web/2020/http://igg.cas.cn/xwzx/yjcg/200903/t20090324_2066956.html"},{"id":null,"t":"Xinxin Fang et al., “Stability estimation of ancient cavern chambers with sloping walls and fishtail-shaped pillars in Longyou Grottoes,” Discover Applied Sciences 8:780 (2026), open access.","u":"https://link.springer.com/article/10.1007/s42452-026-08796-7"},{"id":null,"t":"Longyou Caves Scenic Area, official visitor site, “Discovery” page (English and Chinese versions; secondary, site operator).","u":"https://longyou-caves.cn/en/discovery"},{"id":null,"t":"Longyou Caves Scenic Area, official visitor site, “Structure” page (secondary, site operator).","u":"https://longyou-caves.cn/en/structure"}],"sum":"Four pumps ran for seventeen days. In June 1992, Wu Anai and three other villagers in Shiyanbei, a farming village in eastern China, had decided to empty a pond that local stories called bottomless. As the water dropped, stone walls began to show. On 25 June a huge chamber came into view, its roof held up by pillars, every surface scored with neat rows of chisel marks. No one in the village had known it was there. No book, no map, no inscription had ever mentioned it.\n\nIt was the first of the Longyou Caves, also called the Xiaonanhai Stone Chambers, cut into Fenghuang Hill about three kilometres north of the town of Longyou, beside the Qu River in Zhejiang Province. Within months the villagers had drained five ponds and found five great halls, and investigation soon revealed 19 more caverns nearby, 24 in all in a small area. The site's operators say more than 50 caves are now known along the river, and a second cluster, at Niuchang about 1.7 kilometres away, carries the same kind of tool marks.\n\nThe scale is hard to take in. According to the Chinese Academy of Sciences, summarising a 2009 study led by Li Lihui, the five main chambers have spans of 18 to 34 metres, the widest longer than a tennis court, and heights of roughly 10 to 20 metres, the height of a building of three to six storeys. The operators give even larger figures: a maximum height of 30 metres, a largest floor of 3,000 square metres, and in total about 900,000 cubic metres dug out, some 4.6 million tonnes of stone. Those are visitor-site numbers, not a study's, but even the cautious figures are immense. The average cave floor covers more than 1,000 square metres, and together the caves cover more than 30,000.\n\nThey were cut into argillaceous siltstone, a fine, muddy sandstone of the Upper Cretaceous Quxian Formation, soft enough to carve by hand and soft enough, one would think, to collapse. Most chambers keep two to five great pillars left standing in the living rock, with a distinctive fish-tail cross-section, broad and square toward the entrance and narrow and pointed toward the back. The ceilings slope. The rock above some halls is only 0.6 metres thick, about the length of a man's arm. Stairs are cut into the rock.\n\nThen there is the finish. Ceilings, walls and pillars are all worked the same way, in parallel bands about 60 centimetres wide, each filled with parallel chisel strokes set at an angle of about 60 degrees. It is the kind of uniformity that suggests a rule followed by many hands over a long time. Whoever directed this work cared about how it looked.\n\nWhen was it done? Pottery found in the silt in Chamber 2 belongs to the Western Han dynasty, which ruled from 206 BCE to 9 CE; the operators date pottery shards from the sediment to between 206 BCE and 23 CE. Engineers Zhifa Yang, Zhongqi Yue and Lihui Li put the caverns at some 2,000 years old. That makes the pottery a floor, not a ceiling: it shows the caves were already open by the Han period, and digging may have begun earlier. The operators' English page points to the late pre-Qin to Western Han period, and a scholar at Zhejiang University has proposed that the work began under the Western Han emperor Xuan.\n\nWhich is what makes Longyou so strange. Moving millions of tonnes of rock required organisation, food, overseers, and an authority able to command them for years. Yet, as the operators note, despite China's long written tradition, no surviving text clearly records the project. The caves do turn up in a seventeenth-century poem by Yu Xun, more than fifteen centuries after the Han. Someone decided this work would leave no trace in the archives, or no one thought it worth recording, and it is hard to say which is stranger.\n\nThe mainstream view is plain and reasonable. The caves are ancient human work, cut by hand, most likely as quarries or for storage, around the Qin and Han eras. Their purpose is undocumented. The engineers who have studied them treat them as skilled, planned excavation. In a 2026 study, Xinxin Fang and colleagues modelled a cave at Niuchang 12.5 metres across and found that the sloping roof and fish-tail pillars reduce sagging and stress compared with a flat roof and square pillars. The ancient design, they concluded, gives better long-term stability. The builders knew what they were doing.\n\nThat knowledge is itself the puzzle. The Academy's summary points out that China's own modern rock-support code expects unsupported openings of only 5 to 10 metres in weaker rock to need reinforcement. The Longyou halls are two or three times wider, with roofs far thinner, and they stood for more than 2,000 years. That, the summary says, poses a fresh challenge to modern rock mechanics.\n\nPart of the answer turned out to be the water that hid them. The engineers found that water had filled the caverns for centuries, and its weak acidity, meeting the weakly alkaline rock, kept them stable. Once drained, the five opened caverns began to crack, seep and shed small falls of rock, and a study in the Chinese Journal of Rock Mechanics and Engineering found failures in the vaults and pillars and called for reinforcement. The ponds had been guarding the caves. Draining them to look was the first thing in two thousand years that began to destroy them.\n\nAnd some questions have no engineering answer at all. The caves sit close together, uniform in design and apparently made for the same purpose, yet none of them is connected to another. A small tunnel between two halls would have been trivial next to the labour of cutting either one, and no one dug it. Orderly diagonal finishing is an odd luxury for a quarry, and a hall up to 30 metres high is an odd shape for a storeroom. The operators compare Longyou with the Mogao and Yungang grottoes, which are full of Buddhist art, and with the underground cities of Cappadocia, which were lived in. Longyou has almost no carving. Some 200 kilometres to the north-west, the Huashan Grottoes on the Xin'an River look somewhat similar, but they are likely more than 1,500 years younger.\n\nSo a people who wrote down almost everything carved two dozen cathedrals of rock, finished their walls with care, spanned halls far wider than a modern code would leave unsupported, kept each hall separate from its neighbours, and then left them to fill with water. Was the silence an accident of lost archives, or was it the point, and what did those who cut the halls know about building in stone that we are still working out from their chisel marks?","qs":["Why carve caverns this large and leave no record of the work?","The water may have saved the caves. Should some be flooded again?","Quarries, tombs, storage, or temples: what does the shape of the caves suggest?"],"gal":[{"src":"https://thumb.wikimedia.org/wikipedia/commons/thumb/a/a0/Longyou_Xiaonanhai_Shishi_2016.12.11_16-10-51.jpg/1280px-Longyou_Xiaonanhai_Shishi_2016.12.11_16-10-51.jpg?utm_source=commons.wikimedia.org&utm_campaign=imageinfo&utm_content=thumbnail","page":"https://commons.wikimedia.org/wiki/File:Longyou_Xiaonanhai_Shishi_2016.12.11_16-10-51.jpg","title":"Longyou Xiaonanhai Shishi 2016.12.11 16-10-51.jpg","lic":"CC BY-SA 4.0","licurl":"https://creativecommons.org/licenses/by-sa/4.0","by":"Zhangzhugang","cap":"小南海石室 2号洞","alt":"Longyou Caves"},{"src":"https://thumb.wikimedia.org/wikipedia/commons/thumb/1/1a/Longyou_Xiaonanhai_Shishi_2016.12.11_15-49-15.jpg/1280px-Longyou_Xiaonanhai_Shishi_2016.12.11_15-49-15.jpg?utm_source=commons.wikimedia.org&utm_campaign=imageinfo&utm_content=thumbnail","page":"https://commons.wikimedia.org/wiki/File:Longyou_Xiaonanhai_Shishi_2016.12.11_15-49-15.jpg","title":"Longyou Xiaonanhai Shishi 2016.12.11 15-49-15.jpg","lic":"CC BY-SA 4.0","licurl":"https://creativecommons.org/licenses/by-sa/4.0","by":"Zhangzhugang","cap":"小南海石室 5号洞","alt":"Longyou Caves"},{"src":"https://thumb.wikimedia.org/wikipedia/commons/thumb/1/1f/Longyou_Xiaonanhai_Shishi_2016.12.11_15-53-34.jpg/1280px-Longyou_Xiaonanhai_Shishi_2016.12.11_15-53-34.jpg?utm_source=commons.wikimedia.org&utm_campaign=imageinfo&utm_content=thumbnail","page":"https://commons.wikimedia.org/wiki/File:Longyou_Xiaonanhai_Shishi_2016.12.11_15-53-34.jpg","title":"Longyou Xiaonanhai Shishi 2016.12.11 15-53-34.jpg","lic":"CC BY-SA 4.0","licurl":"https://creativecommons.org/licenses/by-sa/4.0","by":"Zhangzhugang","cap":"小南海石室 5号洞","alt":"Longyou Caves"},{"src":"https://thumb.wikimedia.org/wikipedia/commons/thumb/6/69/Longyou_Xiaonanhai_Shishi_2016.12.11_15-56-30.jpg/1280px-Longyou_Xiaonanhai_Shishi_2016.12.11_15-56-30.jpg?utm_source=commons.wikimedia.org&utm_campaign=imageinfo&utm_content=thumbnail","page":"https://commons.wikimedia.org/wiki/File:Longyou_Xiaonanhai_Shishi_2016.12.11_15-56-30.jpg","title":"Longyou Xiaonanhai Shishi 2016.12.11 15-56-30.jpg","lic":"CC BY-SA 4.0","licurl":"https://creativecommons.org/licenses/by-sa/4.0","by":"Zhangzhugang","cap":"小南海石室 5号洞","alt":"Longyou Caves"},{"src":"https://thumb.wikimedia.org/wikipedia/commons/thumb/f/f0/Longyou_Xiaonanhai_Shishi_2016.12.11_16-07-21.jpg/1280px-Longyou_Xiaonanhai_Shishi_2016.12.11_16-07-21.jpg?utm_source=commons.wikimedia.org&utm_campaign=imageinfo&utm_content=thumbnail","page":"https://commons.wikimedia.org/wiki/File:Longyou_Xiaonanhai_Shishi_2016.12.11_16-07-21.jpg","title":"Longyou Xiaonanhai Shishi 2016.12.11 16-07-21.jpg","lic":"CC BY-SA 4.0","licurl":"https://creativecommons.org/licenses/by-sa/4.0","by":"Zhangzhugang","cap":"小南海石室 2号洞","alt":"Longyou Caves"}]},"img":null,"md":null,"hh":null,"hs":{},"lh":{"s":"img/h/CHN-LON.webp","w":1280,"h":853,"o":"https://thumb.wikimedia.org/wikipedia/commons/thumb/a/a0/Longyou_Xiaonanhai_Shishi_2016.12.11_16-10-51.jpg/1280px-Longyou_Xiaonanhai_Shishi_2016.12.11_16-10-51.jpg?utm_source=commons.wikimedia.org&utm_campaign=imageinfo&utm_content=thumbnail"}}