When Will Hunt was 16 years old, he discovered an abandoned tunnel that ran beneath his house in Providence, Rhode Island, beginning a lifelong fascination with all things subterranean. Here Hunt tracks the origins of life with a team of NASA microbiologists a mile beneath the Black Hills, camps out in the catacombs and sewers of Paris, descends with an Aboriginal family into a 35,000-year-old mine in the Australian outback, and glimpses a Paleolithic sacred sculpture in the depths of a cave in the Pyrenees. Blending mythology, anthropology, neuroscience, and literature, this NPR Best Book of the Year reveals how the subterranean landscape has given shape to our most basic beliefs and how we think about ourselves.