Exploring The Secret Underworld of Earth

The source is a podcast interview with Dr. Heinrich Kusch, an Austrian researcher who studies underground facilities and their possible connections to an unknown, prehistoric culture. The conversation revolves around his discoveries, which were published in the books "Secret Underworld" and "Sealed Underworlds", as well as criticism of his theses. The conversation also covers his collaboration with other researchers such as Dr. Rörig, Dr. Neugebauer, and Artiom.