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