Award-winning nature writer Robert Macfarlane takes a dazzling journey into the hidden regions beneath the surface of the world. From the vast below-ground mycelial networks which enable trees to communicate, to the ice-blue depths of glacial moulins, and from North Yorkshire to the Lofoten Islands, this is an epic exploration of the Earth's underworlds as they exist in myth, literature, memory and the land itself. A thrilling new chapter in Macfarlane's ongoing exploration of the relationship between landscape and the human mind.