Ibn Battuta writes of his travels to 14th century Iraq. George Mallory sends a letter home before he attempts the summit of Mount Everest. Charles Darwin confesses his doubts on a voyage that will change all of what we know, and sailors brave howling gales aboard a Cape Horn windjammer.

Jacques Cousteau and William Beebe pioneer the technology that allows us to penetrate the vast, unknown expanses beneath the surface of the worlds oceans and seas; Robert Ballard describes the discovery of new forms of life in the eternal darkness of the Galapagos Rift.