Who could have built such a complex structure 150,000 years ago, at a time when man had barely started using fire?
The Baigong pipes are one of the greatest mysteries of the ancient world. They can be found inside a badly-eroded pyramid located on top of Mount Baigong in the Qinghai Province of northwestern China.
The crumbling pyramid once had triangular entrances on three of its sides but over time, two of them caved in and are currently inaccessible. The one that remains goes deep inside the mountain. Iron scraps and unusually-shaped stones litter the floor, suggesting that long ago, this place saw activity.
The only remaining cave houses an intricate network of metal pipes, with diameters as large as 1.5 feet and as small as a toothpick. Dozens of pipes run straight into the mountain, leading who knows where.
Some of the archaeologists who visited the site speculated the pipework could have once supplied water to the pyramid. Their theory seems to be supported by a multitude of iron pipes found on the shores of nearby Lake Toson. These ones are also available in a range of lengths and diameters, some reaching above the water surface, others buried below.
Intrigued by these out of place artifacts, the Beijing Institute of Geology analyzed the Baigong pipes using a technique called thermoluminescence. This method allowed them to determine when the pipes were last subjected to high temperatures. Analysis showed the pipes must have been crafted over 150,000 years ago.
And the mystery goes deeper. Analysis performed at a government-operated smeltery was unable to determine the exact composition of of the pipes. Although the pipes were made up of ferric oxide, silicon dioxide and calcium oxide, they also contained 8% of an unknown material.