In a small island in the center of a remote Lake Tere-Khol, high in the mountains of southern Siberia, close to the Mongolian border, lies the ruins of Por-Bazhyn (also spelled Por Bajin), a structure that at first glance appears like a fortress. Por-Bazhyn, which means "clay house" in the Tuvan language, has been known since the 18th century, but it wasn’t explored until the late 19th century. Since then the complex has been fascinating and frustrating experts in equal measure, because they are unable to tell who built it and why.

Por-Bazhyn was first explored in 1891 by a Russian archeologist who noticed similarity of the layout of Por-Bazhyn to that of Kara-Balgasun, the former capital of the Uighur empire that ruled for about a century between the mid 8th and 9th centuries. On the basis of this finding, the monument was dated to that time. It was also that first hypothesis, which gave rise to the name "fortress".

Photo credit: www.por-bajin.ru

The first excavations of the site wasn’t carried out until almost 60 years later by another Russian archeologist who saw construction characteristics typical of Chinese architecture from the T’ang Dynasty. Based on an anecdotal evidence, the so-called Selenginsk inscription, the lead archeologist of the excavation S.I. Vainshtein offered that Por-Bazhyn was a defense fortress built by the second Uighur ruler, Boyan-Chur in 750CE. Vainshtein's hypothesis soon became the most widely accepted and disseminated by other investigators, even though it was based solely on speculation.

In 2007, large-scale fieldwork was undertaken by the Russian Academy of Sciences, the State Oriental Museum, and Moscow State University. Archaeologists found clay tablets of human feet, faded coloured drawings on the plaster of the walls, giant gates and fragments of burnt wood, but nothing substantial that could provide a definitive answer as to why the structure was built.

Another mystery is the absence of traces of habitation. Some progress was made when radiocarbon dating suggested that the fortress was built between 770 and 790 AD, which is 20-30 years later than it was believed. Since Boyan-Chur died in 759 AD, it was hypothesized that his son Byogyu-Kagan built the place. Byogyu-Kagan is known to have declared Manichaeism as state religion, and could have commissioned Por-Bazhyn as a Manichaeism monastery, which would explain the isolation. Byogyu-Kagan was however killed in 779 during an anti-Manichaean revolt which would explain why there are no traces of habitation —the monastery never got used. Of course, there are no evidence to support these interpretations.

Por-Bazhyn’s future is but at stake. The structure sits on a bed of permafrost with has been slowly melting over the past century, as a result of warmer temperature, causing the water level of the lake to rise. As the permafrost melts, the structure could collapse into the lake. According to one researcher, this could happen in about 80 years. There are also evidence of damage caused by at least two earthquakes in the past. One of them may have happened during construction in the 8th century, and another catastrophic one after it the abandoned that destroyed the building.

Photo credit: Irina kh/Flickr

Photo credit: sibved.livejournal.com

Photo credit: sibved.livejournal.com

Photo credit: unknown

Photo credit: unknown

Photo credit: sibved.livejournal.com

Photo credit: www.por-bajin.ru

Photo credit: www.por-bajin.ru

Photo credit: www.por-bajin.ru

Sources: Wikipedia / tuva.asia / Siberian Times