On the Auyan-Tepui, one of the legendary table mountains of South America, an international research team penetrates an unknown, mystical underworld: In a labyrinthine cave system, it encounters strange rock formations that look like coral reefs. They are "living stones", colonies of enigmatic microbes, the likes of which were previously only known from prehistoric times. How did these organisms survive here in the darkness? Do they show how life might have evolved on other planets? And what other wonders are there to be discovered in the underground of the tepuis, the "houses of the gods"? A scientific adventure that proves: We don't have to travel all the way to Mars to find fantastic new worlds.