Mount Baigong, southwest of the city of Delingha, China, and in the Southwestern United States.
First reported in 2002, the Baigong Pipes are a series of pipe-like features made of iron inside a cave on Mount Baigong, some of which lead to nearby Lake Toson, while others lead further into the mountain. The pipes are of varying size, and some are as large as 40 centimeters in diameter, and spread around the area for several hundred feet. They are arranged in an apparently organized pattern.
The pipes appear to have been made long before humans discovered the art of smelting. However, they are in an area not known to have ever been inhabited by humans anyway. The pipes are also empty, and the lack of debris suggests that the pipes were once actually worked for whatever they were used for. They are also not perfectly round, and some suggest that they may have been built in such a way that prevents clogging. China’s government hasn’t released much information on the subject, so not many plausible theories have been made.
Navajo Pipes, found in the Southwestern United States.
Both the Baigong and Navajo Pipes are made up of 30 percent ferric oxide and large amounts of silicon dioxide and calcium oxide. Detailed research indicates that they are the result of the dissolution of siderite cements and the redistribution and oxidization of iron by groundwater. They probably don’t have as many students and scientists looking into the phenomenon in China. In the US, they are usually referred to pipes of ironstone within the Navajo Sandstone.
The Fun Theory:
The fun theory is that the areas were once used as a launch tower and base for aliens.
The Probable Theory:
A natural phenomenon.