Buried in the foothills of the Italian Alps, the amazing Temples of Humankind contain all sorts of wonders, including a four-sided pyramid with mirrored walls, rows of polished spheres, and a room called "The Hall of Water" shaped like a chalice. Despite being underground, some rooms have ceilings that are more than 25 feet high.

But these intricate spaces weren't built by trained architects or engineers. Instead, followers of Oberto Airaudi, who founded the Federation of Damanhur, built the temples in secret beginning in 1978. In 1992, the Italian government threatened to dynamite the temples upon discovering their existence, but ultimately left them alone. Today, they still reside in the Damanhur commune, about 30 miles north of Turin.