The Baigong Pipes are a phenomenon in Tibet, just outside the city of Delingha. They appear to be iron pipes embedded into the solid rock and pre-date any human activity in the area - let alone the development of indoor plumbing. They're an example of what some people call OOPARTS (out of place artifacts). The pipes are certainly odd, and so seemingly anachronistic that many conspiracy theorists and paranormal enthusiasts believe that they could well be proof that ancient aliens once visited Earth. The fact that the mountain in which they are embedded looks vaguely like a pyramid also adds fuel to this fire. So, are these solid proof that ancient extraterrestrials once visited our planet and decided that the mountains needed plumbing in? Unfortunately not. It turns out that they're probably just tree roots. In a study of an almost identical features in Louisiana (the above photograph is sandstone found in America formed by similar processes), scientists found that the composition of the cylinders was not uniform, but depended on which layer of soil they were buried. This indicates that they formed over time as the sedimentary rock built up, rather than being manufactured and driven into the ground. It is likely, therefore, that the pipes were formed by the gradual burial of an organic cylinder (like, you know, a tree) that then rotted away to leave the "pipe". Chinese scientists eventually came to the same conclusions when, using atomic emission spectroscopy, they found organic matter embedded within the pipes. All this said, there's aways the chance that this is just how ancient aliens built their weird mountain pipes. You never know.
