On an island in the middle of a remote lake in Siberia, not far from the Mongolian border, lies the fortress of Por-Bajin. Por-Bajin is an archaeological site that dates to the 8th or 9th century. Its walls enclose 7 acres (2.8 hectares), a maze of about 30 buildings.
Despite extensive excavations, little is known about the site or the people who built it. Theories include a Uighur fortress, a palace, and a Manichaean monastery. Further adding to the mystery is the strong influence of Chinese construction and motifs. [photos]