China’s Mysterious Longyou Grottoes: Nobody Knows Who Built These Gigantic Ancient Caverns and Why

Spectacular mysterious ancient caverns that no one really knows anything about. This is Indiana Jones stuff.

Deep within the Fenghuang Hill of China’s Zhejiang province lies an enigmatic labyrinth – the Longyou Grottoes, also known as the Longyou Caves and the Xiaonanhai Stone Chambers. Carved with astonishing precision, these caverns, hidden beneath the earth for centuries, leave archaeologists and historians pondering their origin and purpose. Questions abound regarding the meticulous chiseled patterns adorning every surface and the methods employed in their creation. But despite their monumental scale and intricate design, their creators remain unknown, sparking speculation about the civilization behind their construction.

In June 1992, four farmers from Longyou stumbled upon the caves as they emptied the water from five small ponds within their village. These ponds unexpectedly revealed themselves to be five massive manmade caverns, with subsequent exploration uncovering an additional 19 caverns in the vicinity. They together cover a a whopping 30,000 square meters (322,917 ft sq).

The first surprise came when the water accumulated in these caverns over an extended duration was pumped out. It was immediately established that that they were not the exceptionally deep “bottomless ponds” common in villages throughout southern China, usually abundant with easily caught fish. Instead, they revealed themselves to be artificial constructs, and to the astonishment of those involved, upon draining the first cave, not a single fish or any other sign of life emerged.

Another surprise followed when it became evident how big these caverns actually are. Carved from sandstone, each grotto measures up to 30 meters (98 ft) deep and boasts a network of pillars, bridges, and gutters. Estimates suggest that over 1 million cubic meters of rock were removed during their creation. Considering the tools and technology of the time, some experts believe that carving such enormous chambers would have been a monumental task, even for a large workforce. Taking the average daily digging rate per person as a basis, scientists have estimated that it would require the continuous effort of 1,000 individuals, working day and night, for six years to finish such a grandiose project.

And these calculations don’t even take into account the elaborateness and precision by which the grottoes were made, only the hard digging required. The Longyou Caves exhibit magnificent scale and momentous design, showcasing delicate yet scientifically planned construction indicative of superior craftsmanship. Although unconnected to each other, each cave follows a remarkably similar model, pattern, and style, resembling grand halls with steep sides and a consistent 45% incline. The straight walls feature clearly defined edges and corners, with uniformly precise chiseling marks throughout.

“At the bottom of each cave, the ancient [builders] wouldn’t be able to see what the others were doing in the next grotto,” explained Yang Hongxun, an expert at the Archaeological Institute of Chinese Academy of Social Sciences. Nevertheless, “the inside of each cave had to be parallel with that of the other, or else the wall would be holed through. Thus the measure apparatus should have been very advanced. There must have been some layout about the sizes, locations, and the distances between the caves beforehand.”

Using modern equipment and techniques, investigators measured the wall sizes and discovered remarkable precision in the overall construction. The consistency of wall thickness between caves in various sections raises questions about the methods employed and the means by which such accuracy was achieved. This is all the more interesting considering the fact that no tools have been discovered on-site. Also, while nearly a million cubic meters of stone were excavated, no archaeological evidence indicates where this stone was taken or provides any other clues about the construction process.

Moreover, each of the Longyou Grottoes is adorned with meticulously chiseled parallel lines spanning from floor to ceiling, creating a consistent pattern across the caves. The extensive effort required for such precision prompts questions about its purpose. Were these labor-intensive markings purely decorative, or do they hold symbolic significance? Presently, their resemblance to markings on pottery from a nearby museum, dated between 500 and 800 BC, is the only known connection.

The intended use of the Longyou Grottoes adds another layer to the enigma.  Were they grandiose tombs for emperors, elaborate storehouses, or even a sophisticated water management system? The lack of funerary objects or clear structural patterns for any of these purposes leaves archaeologists scratching their heads.

The lack of historical records mentioning the Longyou Grottoes makes pinpointing their creation date even more challenging. While some glazed pottery shards found within the caves suggest activity during the Western Han Dynasty (206 BC to AD 23), experts believe the grottoes themselves could be much older. A recent theory based on lichen growth on the cave walls proposes a possible construction date between the 9th and 16th centuries AD. However, the validity of lichen dating for such ancient structures remains a topic of debate.

Consequently, the builders of the caves remain a mystery. Some scientists argue that the sheer scale of the undertaking suggests it was beyond the capabilities of ordinary villagers, and only an emperor or high-ranking members of society could have orchestrated such a massive project, akin to the construction of the Great Wall. But then, why are there no historical records detailing its construction?

Lastly, one of the most interesting and challenging questions is how the Longyou Grottoes have maintained their structural integrity for over 2,000 years. Despite having walls as thin as 50 centimeters (20 inches) in some sections, there are no indications of collapse, debris piles, or structural damage. Throughout centuries of floods, disasters, and conflicts, while the surrounding landscape transformed and exposed rocks weathered, the Longyou Caves have retained their intricate form, patterns, and markings with remarkable clarity. In fact, they appear almost as if they were constructed just yesterday, sparking our imagination even further.

If you found this interesting, also read our article about another monumental undertaking of ancient China, the Yangshan Stele, which was meant to be largest headstone ever erected, but was never finished due to the laws of physics.

Sources: 1, 2, 3, 4