Journey To The Center Of The Earth By Jules Verne

An adventurous geology professor chances upon a manuscript in which a 16th-century explorer claims to have found a route to the earth's core. Professor Lidenbrock can't resist the opportunity to investigate, and with his nephew Axel, he sets off across Iceland in the company of Hans Bjelke, a native guide. 

The expedition descends into an extinct volcano toward a sunless sea, where they encounter a subterranean world of luminous rocks, antediluvian forests, and fantastic marine life — a living past that holds the secrets to the origins of human existence.