9. Por Bajin, Siberia
High in the mountains in the middle of a lonely Siberian lake, scientists discovered the most mystifying archaeological site in Russia in 1891. Por-Bajin (which means “Clay House “) is a 1,300-year-old structure of 7 acres that takes up most of the small island on which it sits. Containing a maze of over 30 buildings, its high outer walls sit only 30 kilometers (20 mi) from the border with Mongolia. But over a century since its discovery, archaeologists are no closer to understanding who built this structure or why.
At first, researchers thought Por-Bajin was an ancient fortress of the Uighur Empire, nomads who ruled southern Siberia and Mongolia from 742–848. It’s constructed with a Chinese architectural style from that time. However, it’s so out of the way of trade routes and other settlements that competing theories eventually arose. Maybe it was a monastery, a summer palace, a memorial for a ruler, or an observatory for the stars. Evidence is accumulating that a Buddhist monastery was at the center of the complex, although only a few artifacts have been unearthed.
The complex does not appear to have been inhabited for long. Archaeologists found indications of earthquakes that may have caused a fire that burned some of the original site. However, the fire appears to have occurred after the island was abandoned for reasons unknown.