Mundus Subterraneus is the most geological of Kircher's works. This book is notable for containing early plates of the Earth's interior, and views of spectacular eruptions of Mt. Vesuvius and Mt. Etna. Plato's Atlantis is represented as an island in the middle of the Atlantic Ocean. Kircher also examines water and fire cycles--providing detailed explanations of hydrophylacia (modern aquifers) and pyrophylacia (modern magma chambers). Furthermore, this is one of the first books dealing with speleology. Kircher's book is far-ranging in his attempt to avoid the split between science, philosophy and religion.