The Baigong Pipes

Should you happen to visit Tibet anytime soon, be sure to stop by the city of Delingha. It's a town of most extraordinary beauty, nestled on the edge of the Qaidam Basin below a range of Himalayan hills. There you'll find the local residents proudly displaying their most famous distinction. For a few yuan you can probably get someone to take you to see it. Only a short journey outside of town is said to be a cave, and in this cave are a series of ancient metal pipes. These pipes predate all known history, and are embedded into the rock itself. They are said to lead through the very mountain, and connect to a nearby salt lake. The explanation? Ruins of a construction project 150,000 years ago, by alien visitors.

http://skeptoid.com/episodes/4181