From ancient footprints to mysterious earthworks, Graham continues his journey into the past alongside experts and curious minds, including Keanu Reeves.

Graham searches for answers to the questions behind ancient works of art, including 25,000-year-old Amazonian paintings and the megaliths of Rapa Nui.

Graham learns of a stone-shaping technique now lost to history, and explores how ancient Amazonians managed to thrive in an inhospitable rainforest.

Although thousands of miles apart, Graham considers the possible link between the shamanistic use of ayahuasca in the Amazon and tobacco in New Mexico.

At Mexico's Temple of the Sun, Graham experiences the extent of the Mayans' astronomical expertise and investigates their complex calendar system.