We're all familiar with the concept of modern technology having ancient Chinese analogues. But a 2002 discovery in remote Qinghai province is anachronistic enough to constitute an OOPart. Out-of-place-artifacts are so unusual, or found in such improbable contexts, that mainstream science has no plausible explanation for them.

The crystal skulls of Mexico referenced in the latest Indiana Jones movie, the iron pillar of Delhi, and the ancient Greek Antikythera mechanism are examples of OOPart yet to be explained. Like these, the pipes of Qinghai's Mount Baigong suggest a level of technology simply inconceivable for the apparent era of their manufacture. Those open-minded enough to think "extraterrestrial" when searching for a theory, while often dismissed out-of-hand, have like-minded souls in some of the Chinese scientists investigating.

Locals, residing forty kilometers southeast of Qinghai's Delingha city, have known of the pipes for centuries. They credit aliens for their construction, and even have legends of extraterrestrial visitors to Mt. Baigong. Although the stories are met with predictable skepticism, they become harder to laugh off when one takes in the sixty-meter pyramid near the mountain's summit. Superficially, the pyramid could be shrugged off as having been shaped by natural forces. For some reason, however, the structure has not been conclusively studied, at least officially.

Near the foot of Mt. Baigong lie three caves, the largest and most accessible some eight meters high by six meters deep. Inside, spanning from the roof to the back end of the cave, runs a pipe 40 cm in diameter. Another one roughly the same size runs into the earth from the floor, with just the top protruding.
Continue read here:
The Baigong Pipes- Nature or OOPart? | China Expat - China Expat City Guide