Archaeological Wonders: The Unsolved Longyou Caves Mystery

In 1992 while draining water from their ponds, four farmers from Longyou County in the eastern province of Zhejiang in China stumbled across the Longyou Caves, some of the most astonishing underground structures in human history. But who made them and why remains one of the world's most intriguing archaeological enigmas.

18 September 2023

Discovered by chance in 1992 by farmers pumping water from ponds which locals have long-believed were bottomless, the Longyou Caves are a series of twenty-four huge, hand-built sandstone caverns. Remarkably, despite their grandeur and precision, there are no historical records of their construction, origin, or purpose. Estimated to be at least 2,000 years old, these spectacular structures have baffled archaeologists, scientists, geologists, architects, engineers and historians since they were found.

Also known as the Xiaonanhai Stone Chambers, it turns out that the ponds weren’t ponds at all. They were the flooded portals to one of the ancient world’s most perplexing mysteries. For over three decades, these Longyou Cave Xiaonanhai chambers have sat unexplained. Who built them? How and why were they built? For such a vast and complex undertaking, why is there no historical record of their existence?

These, and many other questions about the underground monuments add to the intrigue surrounding the Longyou Caves mystery. Let’s take a trip below in an effort to shed light on these curious colossal caverns.

Underground China: Mystery Caves with No Answers

Spanning a vast area, the man-made subterranean chambers of the Longyou Caves appear – at first glance – to be an ancient construction project. The intricacies of their design, characterised by uniform architectural plans, large pillars, intricate carvings, and stairways, are astonishing in their sheer detail and scope.

As the first ponds were drained, five caverns appeared. During further excavations, another nineteen of the Longyou Caves were unearthed, making twenty-four in total. The excavated area is estimated to be around 30,000 square metres and the average floor area of each cave is over 1,000 square metres, with heights varying from ten to thirty metres.

The excavated area is estimated to be around 30,000 square metres and the average floor area of each cave is over 1,000 square metres, with heights varying from ten to thirty metres.

These stone chambers are notable for their almost uniform design. None are interconnected, and despite some having extremely thin walls, they have maintained their structural integrity. They have straight walls and ceilings, with pillars supporting the roof. The chisel marks left on the walls and ceilings are consistent across the caves, indicating a systematic, organised method of construction.

Each fully-formed cave possesses a single entrance linked to a vertical shaft featuring a sculpted staircase, allowing rainfall and surface runoff to flow into the caverns. To regulate this water influx, the cave’s base was designed with a series of drainage grooves, channels, and a water catchment system. This in itself raises a most perplexing question. Did the ancient architects who built the Longyou Caves have an advanced understanding of drainage, water management and hydrology?

Even the method and tools used for their creation remain speculative, given that such monumental work would have required a level of architectural knowledge and engineering skill far advanced for its time.

The Birds and the Rocks

The caverns were constructed below what is now known as Fenghuang Hill. The fenghuang is a bird and one of the most revered creatures in Chinese mythology and culture, often equated with the Western phoenix. Symbolising high virtue, grace, and the union of yin and yang, its influence is deeply entrenched in various aspects of Chinese art, literature, and cultural practices. Is there a connection between the mythological creature and the Fenghuang Hill Caves?

As well as high virtue, grace, and yin and yang, the fenghuang is also associated with rebirth and royalty. Were the caves built as a place of balance, peace, or spiritual importance? Were they used for important religious or cultural ceremonies or even tombs for the elite?

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The choice of location for the Longyou caves, Fenghuang Hill, might have been considered auspicious. In ancient cultures, geographical features often played a significant role in determining construction sites, especially for projects of great significance. The association with the revered fenghuang might have been believed to bestow the site with special energy or protection.

Yet, like all other theories about the purpose of the Longyou Caves, mystery reigns. They remain hypothetical in the absence of concrete archaeological or historical evidence.

On a more practical note, it has been estimated that around one million cubic metres (over 350,000 tonnes) of rock was excavated to create the caves by hundreds, if not thousands, of workers, each with their own tools. One estimate suggested a thousand people working day and night would have taken six years to complete the project. Yet not a single piece of rock has been found in the local area, nor a single tool or a shred of conclusive evidence anyone was ever there.

Between a Rock and a Hard Place

Stalactites and stalagmites eveloping underground caves. (Credit: travel and editorial image via Getty Images)

The Longyou Caves, due to their vastness and intricacy, have posed numerous questions that remain largely unanswered. While several theories have been proposed, none have been definitively proven.

What Was the Purpose of the Caves?

Some researchers have suggested they may have been used for reasons as varied as grain storage, as a mine for natural resources, as observatories for astronomical or astrological purposes, for ceremonial or royal rituals, or as shelters against invaders or natural disasters.

Who Built the Caves?

The identity of the builders remains a mystery. Given the age of the caves, they’re believed to have been constructed around 200 BC, they could be the work of a yet-to-be-identified ancient Chinese civilisation.

Where is the Rock?

Disposing of 350,000 tonnes of sandstone isn’t an easy task today. Two thousand years ago it would have been near-on impossible. Some have suggested it was repurposed for construction elsewhere (although there’s no evidence to suggest that’s true), or over many years, the excavated material might have been removed in small quantities and carefully dispersed, leaving no significant piles of debris behind.

Why is there no Historical Record of the Longyou Caves?

It’s possible there may have been written records of the Longyou Caves Xiaonanhai chambers but they could quite easily have got lost or destroyed over the intervening two millennia. It’s equally possible that the caves might have served a purpose that was intentionally kept secret or sacred, leading to its omission from records.

While these theories provide a variety of possibilities, the true origins, purpose, and methods behind the Longyou Caves remain a mystery.

Unearthing the Past: The Enduring Mystery of the Longyou Caves

One of the largest and most complex excavation projects in the history of the ancient world is also one of its greatest mysteries. In the far reaches of eastern China, these mystery caves have dumbfounded every expert who’s seen them. With their vast chambers and meticulous carvings, they stand as a testament to the prowess of ancient builders whose identity and purpose remain shrouded in bewilderment.

While speculative theories abound, the Longyou Caves mystery challenges the understanding of ancient Chinese engineering and culture. The absence of definitive historical records only deepens the enigma. As one of the most intriguing archaeological wonders of history, the caverns invite scholars, historians, and curious minds alike to unravel their secrets.


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