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Siberia’s Incredible 1,300 Year Old Mystery Fortress

Written by Laura Davies

Por Bazhyn is a 1,300-year-old isolated fortress, surrounded by 10m high walls in one of the most inaccessible areas of the Republic of Tuva in Siberia. Built on a small island in the centre of Lake Tere-Khol, high in the mountains, it’s been cut off from all civilisation and well preserved. Despite this, when, why, and how it was built has left scientists and archaeologists baffled for over 100 years. When Vladimir Putin visited in 2007, he left saying, “I have been to many places, I have seen many things, but I have never seen anything of the kind.”
It was first investigated by Russian geographer and ethnographer Dmitry Klements in 1891 and excavated in the 1950s and 60s by archaeologist Sev’yan Vainshtein. They were able to prove that it was built during the Uyghur Khaganate period in the 8th century, but not much more. Despite the huge amount of work that would’ve gone into such a massive project in the remote location, they were unable to uncover much of a cultural layer at all. Meaning it was never used.


How was it Built?

Before we even get to why it was built, the first mystery to solve was how. It’s a 7.5-acre site, with more than 30 separate buildings, and it occupies almost a whole island in the middle of Lake Tere-Khol. Just getting the materials across the water and finding enough space for the builders to work would’ve been challenging enough without the -45oC winters and +40oC summers.
Local legend gave the first clue to solving this one, though. It’s said that in ancient times, there was no lake surrounding the fortress, and a boy, Khan Osel, was born there with ears like a donkey. One morning, he saw water pouring from a well. He was frightened and quickly fled to the mountains with his servants. When they turned and looked back, they saw a huge lake had appeared, surrounding Por Bazhyn. It got its name, Tere-Khol, when Khan got up, waved his hand towards the lake, and cried out in alarm: “Ter hol, Ter hol!” “Ter” in Mongolian means “this,” while “hol” in Tuvan means “lake”.
Scientists set out to investigate, and while the donkey ears remain unproven and largely irrelevant to the story, the sudden filling of the lake is not as farfetched as it sounds. A study of the area with satellites revealed that the water level has both increased and decreased over relatively short periods. Almost completely disappearing on several occasions, most likely due to earthquakes cutting off or diverting the underground springs that feed it. At the time of Por Bazhyn’s construction, the lake was severely depleted and the fortress was built on a peninsular, not an island.

Why was it Built?

So, why was it built? Let’s start with what the archaeologists knew. In Tuvian, the name Por Bazhyn means “clay house,” but with 30 buildings, it was clearly much more than this. They also knew the rough date of construction, sometime in the 8th century, the time when the Uyghurs ruled the region. Finally, the layout bore a striking resemblance to that of Ordu-Baliq, the palace and capital of the Uyghur Khaganate.

The Uyghur Khaganate was a Turkic empire that covered much of central Asia between 744 and 840 AD. It began life as an alliance between the nomadic tribes of the area, who’d spent centuries fighting for either control of the region or simply the right to live there freely. The Uyghurs were just one of these tribes. However, through a seemingly endless list of alliances both made and broken, victories over fellow tribes and the destruction of the Turkish Khaganate in 744AD, they came out on top and formed a kingdom. The Uyghur Khaganate.
So, to archaeologists, it was fairly clear that Por Bazhyn had been constructed by the Uyghurs. What no one could figure out was why. What could it possibly have been used for? Of course, there were theories. The three most plausible being a fortress, palace, or monastery.


Was it a Uyghur Khaganate Fortress?

The volatility of the region, and the sheer number of conflicts in Central Asia at the time, led some to conclude that a fortress made the most sense. And in fairness, Por Bazhyn looks like a fortress. The rectangular-shaped construction covers almost the entirety of the island, leaving the lake as a natural moat, and the outer walls are 10m high with bastions and the remains of a wooden fighting platform. I mean, it just screams defensive structure.
However, there’s a major flaw in this theory. If it was built as a defensive structure, what was it there to defend? Seriously, I cannot emphasise enough how remote this place is. Initial hypotheses suggested it could’ve acted as a guard post on the Great Silk Road between China and Europe. However, even the most northerly branches of the road were still about 1000 km south of Por Bazhyn. As was everything else. There were no military bases, valuable resources or even a food warehouse anywhere near the site.

Was it a Uyghur Khaganate Palace or summer house?

So perhaps it wasn’t built for war, but for peace. To get there we have to look at what happened over the next couple of years in the Uyghur Khaganate.
Following the destruction of the Turkish Khaganate, the leader of the Uyghurs, Qullığ Boyla, took the title Kutlug Bilge Kol Khagan (Glorious, wise, mighty Khagan) and claimed himself as the supreme ruler of all the tribes. He died just three years later, in 747AD, leaving the empire to his son, Bayanchur Khan. This began a period of rapid expansion and the golden age of the Uyghur Empire. Bayanchur Khan brought more tribes under Uyghur rule and built strong alliances with the neighbouring Chinese Tang dynasty.
Most notably, he sent 4000 horsemen to aid Emperor Suzong during the rebellion of 755AD. They were used to retake Chang’an and Luoyang and were handsomely rewarded. Not only did the Uyghur take home all the silk they could find in Luoyang after 3 days of post-battle looting, the Tang gifted them an additional 20,000 rolls, honorary titles, a fixed horse trade price of 40 rolls of silk per horse, and guest status when visiting Tang China. Their bond was strengthened further with an exchange marriage. Bayanchur Khan married Emperor Suzong’s daughter, Princess Ningguo and Bayanchur’s daughter, Princess Pijia married Tang dynasty Prince Li Chengcai.
What do you do when you’ve married a princess? Build her a palace, of course. Specifically, one that would celebrate her Tang heritage and allow her to be comfortable. The striking similarity of the architecture of Por Bazhyn to the Chinese Tang style buildings had already been noted by archaeologists. In particular, the northern curtain wall looked to have been constructed using the hangtu rammed earth method. This involved the construction of a temporary frame, adding a layer of earth, pounding it to condense it as much as possible, and repeating until the wall was completed. Some ceilings were also constructed using the dougong method, or the Chinese nailless ceiling technique. A series of brackets, dous and gongs, were stacked and interlocked on top of columns to support the weight of the roof.
Por Bazhyn does, however, lacks any form of heating system and, in a climate where winter temperatures can drop to -45oC it’s unlikely to have been designed for year-round use. So, maybe it was less of a palace and more of a summer house. This is given dubious weight by the fact that local residents claim the family and their warriors enjoyed resting on the island so much that on dark nights you can still see the 8th-century ghosts on horseback visiting their favourite rest house even after their deaths.
Of course, there are a few holes in this theory too, beyond the fact that ghosts are being used as supporting evidence. Firstly, the architecture that was attributed to Tang culture has now been proven to be of a distinctly Uyghur style. Secondly, Princess Ningguo only ended up staying with the Uyghurs for 6 months in 758AD, as Bayanchur died shortly after their marriage. This wouldn’t have been enough time to complete the palace, and the princess didn’t stay in it alone, because the Uyghurs wanted her to be buried alive with her husband instead. The Tang, understandably, objected to this plan, and after some tense negotiations, she was allowed to leave.


Was it a Uyghur Khaganate Monastery?

Neither fortress nor palace was a great fit, but without further evidence, it seemed like a mystery that would be left unanswered. However, in 2012, Fusa Miyake, a cosmic ray physicist at Nagoya University in Japan, published findings in the journal Nature that would not only solve this mystery but have the potential to solve many others worldwide.
Since the late 1940s and the work of Willard Libby, we’ve used radiocarbon dating to calculate the year of death of any organic material found. Carbon exists in the atmosphere in 1 of 3 forms; 12 and 13, which are stable, and 14, which is radioactive and therefore has a half-life. Carbon 14 is made when cosmic rays enter Earth’s atmosphere, producing neutrons that collide with nitrogen 14 atoms, creating carbon 14 and hydrogen atoms.
Plants and animals continually take in all three types of carbon through photosynthesis and their diets for as long as they’re alive. This refreshes the carbon 14 atoms in their cells. However, when a living thing dies, it stops replacing its carbon, and the amount of radiocarbon present in its tissues steadily declines. As we know the half-life of carbon 14 and that it decays at a constant rate, it’s, therefore, possible to establish an estimated date of death by measuring the residual amount of radiocarbon left in the tissue when found thousands of years later.
The only issue is, it’s not always that accurate. Sometimes, only narrowing down the time of death to within a decade or century. While in most cases, this isn’t too problematic, in the case of Por Bazhyn it’s vital. If the fortress was built before Bayanchur Khan married the princess, or after his death, a 1-year window, it couldn’t be a palace made for her. Archaeologists needed to know the exact year of construction. Miyake’s work did just this.
In the past, scientists believed that the amount of cosmic rays, entering Earth’s atmosphere and creating carbon 14 was fairly constant, varying between 1 and 2%. Miyake discovered this wasn’t true. When studying the tree rings of an 1800-year-old cedar, she found a surge in radiocarbon in 775AD of 12% and in 994AD of 9%, which can only have been caused by an intense burst of cosmic radiation. These events were named Miyake events after their discoverer, and they can be used to conduct what’s called wiggle matching. This can determine the exact year a tree was cut and, therefore, the construction date of thousands of previously inaccurately dated buildings.
For example, scientists have already used the events to establish the exact date of construction of a Swiss Chapel (Holy Cross chapel of the convent St. John the Baptist in Val Müstair, Switzerland). They’ve also conclusively proven that Vikings, and not Christopher Columbus, were the first Europeans to reach the Americas. Wood samples taken from L’Anse aux Meadows in Newfoundland were known to have been cut by Norse explorers as it’d been done with metal weapons. This and the Icelandic Sagas indicated that the Vikings had beaten Columbus, but it couldn’t be proven or known by how much. With the help of Miyake events, the case is now closed. The Vikings won by 471 years.
This precise dating, therefore, has the potential to adjust or completely rewrite huge portions of human history. But what did it do for Por Bazhyn?
In 2018, Russian scientists obtained samples of larch from the walls of the fortress with reliable bark layers and sent them to the University of Groningen in the Netherlands, one of the world’s leaders in carbon dating. There they discovered the Miyake event in the 3rd ring of the sample, providing conclusive evidence that construction began in the summer of 777AD.
This discovery meant that researchers had been basing all their Por Bazhyn theories on the wrong Khagan. Bayanchur Khan died in 759AD. Instead, they should’ve been looking at his son, Tengri Bögü Khan (the Third Khagan of Uyghurs).
After taking power in 759AD, Tengri, who was as up for a fight as his dad, didn’t waste much time before planning to invade the Tang with 4000 soldiers in 762AD. However, following negotiations, he joined them instead, and the Uyghurs helped, once again, in defeating the rebels at Luoyang and, again, looted the city. Unfortunately, he went one step further than his father and chased the fleeing citizens to the Buddhist temples they’d fled to and burned them down. 10,000 people were killed before the Tang paid them 100,000 pieces of silk to get them to leave.
This period is significant because during the campaign he met Manichaean priests who converted him to Manichaeism. A dualistic religion based on the cosmic struggle between good and evil, which Tengri soon declared the official religion of the Uyghur Khaganate. This supports the final theory for the reason for Por Bazhyn’s construction, as a new official religion would surely warrant a new monastery. What it doesn’t explain, however, is why it was left unused and abandoned just 2 years after it was built.


Why was Por Bazhyn Unused and Abandoned?

To conclusively prove Por Bazhyn was built for religious purposes, this last question must be answered, and to do this, we need to know what happened next in the Uyghur Khaganate.
In 779AD, Tengri Bögü Khan decided, once again, to invade the Tang dynasty, this time under advice from the Manichean clergy. His uncle, Tun Baga Tarkhan, disapproved of the religion and strongly opposed the plans. He tried to reason with Tengri.
‘The Tang is a great state, and it never betrayed us. Last year, we invaded Taiyuan and seized several tens of thousands of sheep and horses. We could count that a great victory. But because our way back was difficult and obstructed, by the time we reached our home, we were suffering from wounds, were tired and almost exhausted. If we mobilise our forces again and do not gain a victory, how will we return at all?’
His pleas were unsuccessful. While you might be thinking that this Tun Baga Tarkhan sounds like a reasonable guy and his anti-war sentiments seem to set him apart from his violent family, you’d be wrong. When reason didn’t work, he had Tengri killed along with 2000 of his family members and followers and declared himself Khagan. Fairly on brand.
Once ruler, he began to suppress the Manichean religion, providing the final piece of the puzzle for Por Bazhyn. Clearly, he’d have no need for a Manichean monastery, and so it was abandoned, having never been used. He ruled for 10 years until his death in 789AD, and Manichean did eventually make a comeback as the official religion. However, by then the monastery had been hit by 2 earthquakes and a fire. Restoration would’ve seemed futile as the potential for further earthquakes would’ve undone any work and made it unsafe for habitation.


What will Become of Por Bazhyn?

In 2004, the government of Tuva announced plans for the development and preservation of culture in Tuva. They included Por Bazhyn in their program, and they aim to restore the site and create a Por Bazhyn Fortress Park. However, geology is not on their side. More threatening than the earthquakes or fires, Por Bazhyn is built on a permafrost plug, isolated in the centre of the unfrozen lake. Each year, the edges of the permafrost thaw and the shores of the island erode. Geologists predict Por Bazhyn has only 150 more years before the outer walls collapse, marking the beginning of the end for the monastery.
By Laura Davies


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