Jaw-dropping pictures of Siberian ruins as new royal theory may explain this remote 7th century summer schloss.
It is among the most mysterious palazzos anywhere, and although it is located at 'the very centre of Eurasia' - presumably by chance not design - it must be one of the most inaccessible.
Rapid erosion of its breathtaking but vanishing grandeur may, before too long, deprive archeologists of the opportunity to prove why this place, known as Por-Bajin, was built, and who by. Or should the question should be: who for?
Erected on an island in Lake Tere-Khol by - probably - 757 AD , the palace, close to the present-day Russian border with Mongolia, has long fascinated yet frustrated experts in equal measure, but now we may be edging closer to answering the questions that have for so long perplexed scientists.
When it was constructed, Por-Bajin was nowhere near the hub of any civilisation, nor on a known ancient trade route. One fact seems abundantly clear, and deepens the riddle of this lavish mountain retreat: no-one ever lived here.
Another is that it was designed solely for summer living. Some 2,300 metres above sea level in the mountains between the Sayan and Altai ranges, archeologists say no allowance was made for the bone-chilling cold of winter.
Yet it had been scrupulously built to the demanding edicts of its ancient designers: for example, the towering outer walls were ten metres tall and 12 metres wide. They were planned to be impenetrable.
It has been described as 'a kremlin-like fortress' with its centrepiece a structure the inner courtyard supported by no less than three dozen wooden columns resting on stone bases.
Archaeologists found clay tablets of human feet, faded coloured drawings on the plaster of the walls, giant gates and fragments of burnt wood in what has been hailed as 'one of the most mysterious archaeological monuments of Russia'. Laser mapping helped experts build a 3D model of what the palace - on a 3.5 hectare site - might have looked like in its heyday.
Russian ethnographer Dmitry Klements, who examined the ruins in 1891, believed it to be an Uighur fortress, a view echoed by Soviet archaeologist Sevyan Vainshtein, who conducted the excavations on the site in the decade following 1953. Another theory, later discounted, was that this was a Budhist monastery. One more idea was that it was an astronomical observatory.
Vainshtein believed that ancient Uighur inscriptions found close to the Selenga River - which flows into Lake Baikal - are clues about this place. They refer to 'whitish camp and palace with a throne' yet there was no mention of the lake, which might have been artificial, according to some authorities.
Experts believed it could be the the summer palace of Uighur ruler - or Kha Khan - Boyan-Chor. Yet research involving archeological excavations begun in 2007-08 on the initiative of the Russian Defence Minister Sergei Shoigu - a native of Tuva, also known as Tyva - now questions this version.
The scientists established that there was almost no 'cultural layer' on this site. Hardly any evidence of man's presence here was found. Hence the conclusion that the VIP for whom it was built never lived here. Nor did anyone else.
Head archeologist Irina Arzhantseva said: 'If the Kha Khan with his wife and servants had spent at least one summer in the fortress, or monks had lived here, they would have left a layer of soil, landfills, full of artifacts. However, the ancient floors uncovered during the excavations are almost not disturbed.
'Only one pit was found containing debris, where we located one single silver earring with a pendant - very typical men's jewellery for Turks at this time. Fragments of three to four ceramic vessels were found at the gate, on the ramp. Perhaps a guard or builders left them.' There was no heating system nor fireplace in a place with a harsh winter climate: this was evidently only a summer schloss.
Geomorphologists found convincing evidence that disputed the claim that the lake was artificial. It is entirely natural, a fact which increases admiration for the ancient builders.
'Drilling of lake's sediment and the determination of their radiocarbon age showed that it appeared long before the construction of the fortress, not less than 11,000 years ago,' said Dr Arzhantseva. A bridge to the fortress was also unlikely: access had been by boat. The materials used to build the lake were taken from the island itself, or the lake bottom, analysis shows.
Yet while no-one ever lived here, not only was this palace fully completed - in other words it was not semi-built and then deserted - but repairs were carried out on it in the years after its erection.
Demir Tulush, research fellow of the Department of Archaeology of the Tuva Institute of Humanities and Social and Economic Research, said: 'Por-Bajin was completed in full. All the buildings were totally built. More than this, the fortress was repeatedly repaired. Lake Tere-Khol is located in a seismically active zone. Regular small and big earthquakes occur there. On the fortress are visible large faults obviously left by the aftershocks.
'And repaired cracks were revealed in the course of the excavation. For at least ten years it was maintained in good condition. But no one lived there.' During the research, scientists using radiocarbon and dendrochronological methods confirmed the palace was built in the decade starting in 770 AD, and this in turn discounted the theory it had been constructed for Kha Khan Boyan-Chor, who, by then, was already dead.
The research also disputed that this was primarily a fortress. Tulush said: 'It was built at a considerable distance from the main commercial and military routes, so there was no sense in the construction of the fortress at this place. Another specific point is its location on an island in the lake. In addition, despite the high walls, it was not attacked, and there were no traces of intentional destruction.'
He concluded: 'It looks like someone built these rather big and complicated facilities - and then abandoned them, not living here at all. It was built gradually, not at once. It was built over several years. Cracks appeared in the walls during the construction, but they were repaired. The main question is - who built this and why it was abandoned? We have several versions.
'The first is that it was a summer palace, and at least its structure is very similar to the known Uighur palaces. But it is located in the remote taiga, so military and administrative management would be difficult from here. It could have been the summer palace built for a Kha Khan's wife', possibly the spouse or intended partner of Byogyu-kagan, son of Boyan-Chor.
'It is known that Chinese princesses could become the wives of Uighur and Turk Kha Khans. Probably, one such princess was destined to live in this palace, but something happened to her on the way here, and she never came to the site, and it was totally abandoned in 30 or 40 years.'
For now, this seems to be the best guess to explain this remarkable palace, and to answer the question who it was built for. A tragic Chinese who died en route to take up residence. But he has another theory, too.
'The other option is that it could be a temple complex, but not Buddhist, rather Manichaean. It is known that most of the Uighurs practiced Buddhism, but the ruling elite took Manichaeism, and in 760s AD, Manichaeism became the official religion of the Uighur Khanate.'
Byogyu-kagan took Manichaeism, but not all the Uighurs supported him. Possibly, this version goes, he wanted to construct a fortified palace-temple to hide there with his coreligionists. The new data of the construction of Por-Bajin coincides with this theory.
Dr Arzhantseva noted: 'In 779 Byogyu-khagan was killed during an anti-Manichaean coup. If Por-Bajin was finished about 778 - 779 AD, just before the coup, the Kha Khan had no time to use it.'
Yet another theory on Por-Bajin has come from Chinese archeologists, who have suggested it could be a memorial, created in medieval Chinese tradition. Irina Arzhantseva said: 'The custom of arranging burials in beautiful places (in the mountains, near water, for example) and support them with a memorial complex was described in written sources of the Tang dynasty.
'The royal tomb itself could be located on top of a neighbouring mountain from where the memorial facilities were clearly viewed. In the case of Por-Bajin, the convenient place for burial could be the top or part way up the mountain on the southwest shore of the lake.' As yet, though, no sign of a royal tomb has been found.
The worrying erosion of the ruins at Por-Bajin is due to climate warming which is melting the permafrost. 'Water from the ground leaks into the soil and the permafrost gradually thaws,' said Tulush. 'In winter, the water freezes and expands. In summer thaws again, forms cavities and the ground collapses.
'I have noticed that in seven years after the excavations were finished, on the west side, the shore of the lake has fallen 8-to-10 metres. We need to take some measures to prevent further destruction, but it requires huge funds.'
Among visitors to the site was President Vladimir Putin who summed up what many feel about this magical palace. 'I have been to many places, I have seen many things, but I have never seen anything of the kind,' he said.
My impressions from traveling to Por Bajin
Beware the spirits of the abandoned palace...'where exotic strippers once danced'
It can take a tortuous 20 hours to reach Po-Bajin from Tuva capital Kyzyl in good weather in an off road vehicle, and several days if conditions are bad. For wealthy tourists, another option is to fly in by helicopter.
Either way, local resident Dorzha Nikitin, 35, who lives on another island in Lake Tere-Khol will be waiting to act as your tour guide, helped by his aide Romeo, dog Strelka and cat Kysa. Between helping visitors, he fishes for pike, which he then smokes to sell to tourists.
Dorzha has his own take on the ancient palace, as he obligingly explains. 'This was a Khan's palace, and here in front of it, danced strippers for his amusement. Behind the palace you see the magnificent taiga, very beautiful.'
He shows bricks with prints of hands and burned wood. Somewhere in the Khan's Palace is hidden a treasure trove, but the spirits forbid it to be dug, he says. 'You cannot take anything from the island, the spirits are strictly against it, he explains.
'Even if you take a stone, then your car will break down on the road. One tourist took a piece of tile and promptly missed his plane. Then a Japanese woman picked up a tile from the floor, and for three days she could not get to Kyzyl. Other bad things happen to them, too, and they get sick and die. We have to call the shamans to ward off the spirits.
'Take the example of Romeo's family. They took the bricks from the island, to build a traditional stove, and then promptly died. Before the excavation, we needed to call the shamans. They made a long rite, lasting almost the whole day long. One told how he saw a vision as if the man lay on top of the fortress, and did not allow it to be dug up. But then he left. And the other saw a throne, on the exact spot where a tree grows.'