Skip to main content
Ages 13+
Under 13
Athanasius Kircher

The Amazing Mundus Subterraneus, By Athanasius Kircher


Inspired by an adventure into the crater in Mount Vesuvius, “the last renaissance man and the master of one hundred art forms” wrote one of the most fascinating books about the interior sinews of our planet.

Athanasius Kircher is one man to know. He was an erudite and the explorer of an entire gamut of academic disciplines. In short, he was one of the sharpest minds of the 17th century (and of all times) who saw in the interior of the earth a sort of alchemical dance between the elements. His masterwork, Mundus Subterraneus, is a spectacular work about the entrails of our planet: a two-volume book of encyclopedic proportions that presents “before the eyes of the curious reader all that is rare, exotic, and portentous, contained in the fecund womb of Nature.”

Under the premise that there is an “idea of the earthly sphere that exists in the divine mind,” Kircher set himself to write this memorable book. Mundus Subterraneus is made up of discussions on the spontaneous generation of animals that sprouted from inert objects, of lists of the immoral sources from which alchemists attempted to transform basic metals into gold, and even of the location of the legendary lost island of Atlantis (something that science hasn’t been able to tell). In addition, the book includes detailed discussions about giants and other animals that live in the underground, including, of course, dragons. But amidst all of the subjects he delved on, his theory on the interior of the Earth is what has most captured the attention of scientists and curious laymen for centuries.

As Kircher himself explains: “the whole Earth is not solid but everywhere gaping, and hollowed with empty rooms and spaces, and hidden burrows.” According to him, the interior of the Earth contains what we could call oceans or lakes of fire interconnected by corridors leading to its very nucleus. He thought then (and now it is confirmed by science) that volcanoes were Earth’s escape valves of pressure, which proves that the planet is indeed full of invisible, underground fires, and that earthquakes are nothing but signs of the internal combustion of the planet.

“The fire and water sweetly conspire together in mutual service,” he said. Thus, hot springs and geysers are produced when the subterranean canals of water and fire interact, pushing the water up through the surface. Sparked by this theory we have one of the most beautiful drawings of the book, in which Kircher sketches the hidden details of its interior cracks and caves, the perfect alchemical system to gestate life.

But Kircher didn’t come up with his ideas by pure speculation; in 1638 he experienced the earth’s internal power first hand on a trip to Sicily to study the volcanoes and caves of the area––he was interrupted by an earthquake that devastated most of the Calabria region. He remembers that the event took place while he was on a boat off the coast of the city: “the sea was raging beyond what is usual, and began stirring up huge whirlpools.” Able to reach shore safely, he then decided to explore Mt. Vesuvius in order to explain the secrets of the tectonic movements of the Earth. Vesuvius was still smoking after the large explosion six years earlier. At the top of the volcano, Kircher looked down into the crater and, as he later wrote: “I thought I beheld the habitation of Hell, wherein there seemed to be nothing besides the horrid phantasms and apparitions of Devils.” He heard “horrible bellowings and roarings” and there was “an inexpressible stink.”

To take refuge from the “inferno,” Kircher took refuge in an ash-filled cave where he found a tunnel that he believed would have led him to the very entrails of the earth.

It was inside this hollow where Kircher began to develop his theories that years later he would include in his Mundus Subterraneus, sketching out the alchemical processes occurring inside the planet and describing how mountains, rivers and oceans are all secretly interconnected. It was a moment of history that opened up a pathway for future scientists to imagine and study the secrets of our planet. To travel to the center of the Earth, as the dreamer and polymath Jules Verne imagined, is just one example of the legacy of Kircher’s magnificent Mundus Subterraneus.

Related Articles